JPS641979B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tuner for a TV receiver that receives a TV signal, selects a desired TV channel, and converts the frequency to an intermediate frequency. there was
This concerns VHF-UHF all channel tuner.

SUMMARY OF THE INVENTION An object of the present invention is to provide an all-band tuner with low noise and low distortion characteristics by minimizing spurious interference caused by channels other than the desired channel due to the double convergence system.

FIG. 1 is a block diagram of a conventionally used VHF electronic tuner.

The input signal from the input terminal 10 is input to the input filter 1.
1, interference signals in the intermediate frequency band, FM signals, etc. that interfere with the TV intermediate frequency signal are removed, and the signal is input to the single tuning circuit 12. Single tuned circuit 1
In step 2, a desired reception channel is selected using one varactor as a variable resonant element, and the signal is input to the RF amplifier 13 and amplified. The amplified signal is input to a demodulation circuit 14 using two varactors as variable resonance elements, unnecessary signals are removed, and the signal is input to a mixing circuit 15. An oscillation signal from a variable frequency oscillator 16 using a varactor is applied to the mixing circuit 15 . A frequency-converted intermediate frequency signal is extracted from the output of the mixer 15 and amplified by the intermediate frequency amplifier 17.

In the conventional tuner as described above, a tuning varactor is required for each of the single tuning circuit, the detuning circuit, and the oscillation circuit, and tracking adjustment between each circuit is required.

Additionally, two circuits are required to receive VHF and UHF TV signals. Additionally, VHF
For low-band and high-band reception, switching diodes are used to adjust the tuning frequency and
and it is necessary to change the oscillation frequency.

In order to eliminate the above-mentioned drawbacks, various double super-heterodyne all-channel tuners have been proposed.

The double super-heterodyne tuner that has already been proposed requires the selection of the output frequency of the mixer on the input side, that is, the first intermediate frequency, and the mixing method in the mixer, that is, the selection of the local oscillation signal (frequency: f _L1 and ) and the received signal (frequency: f _S ) is the first intermediate frequency (f _L1 − f _S = f _IF1 )
Or, the sum of the local oscillation signal and the received signal is the first
There are two methods for setting the intermediate frequency (f _L1 + f _S = f _IF1) , but both of these methods have drawbacks.

These drawbacks will be explained below.

Figure 2 shows the basic circuit configuration of a double super-heterodyne all-band tuner. In the figure, 21 is an input terminal;
22 is a fixed band pass filter on the input side having the required band such as VHF and UHF, 23 is a variable attenuator, 24 is an RF amplifier, and 25 is an amplified high-frequency input signal that selects a desired TV channel. A first mixer 26 is a variable frequency oscillator to select a desired TV channel input to the mixer 25. 27
is selected and frequency-converted first intermediate frequency is used as a selective wave to eliminate interference from other channels in subsequent circuits.
Pass filter 28 is the first intermediate frequency to TV
the second for frequency conversion to the intermediate frequency of the receiver;
The output of the fixed oscillator 29 is input to the mixer. 30 is an intermediate frequency amplifier for amplifying the signal frequency-converted to the intermediate frequency of the TV receiver.

In the above basic circuit configuration, the characteristics of each circuit are very important in determining the overall characteristics of the tuner, and the interference characteristics of the system depend on which frequency is selected as the first intermediate frequency. will change greatly.

Now, the first intermediate frequency is set to the 300 to 400 MHz band (for example, 330 MHz), and the variable oscillator signal (frequency: f _L1 ) input to the first mixer is set as the mixing method of the first mixer. Assume that a method is adopted in which the first intermediate frequency signal (frequency: f _IF1 ) is obtained by the difference between the signal and the high frequency input signal (frequency f _R ).

Considering channels other than the desired channel as the interference signal, the frequency band of the interference signal is, for example, 54MHz to 890MHz in the case of the US TV band. (Hereinafter, the frequency of the interfering signal is abbreviated as f _u .) What first intermediate frequency should be selected for the harmonic interference, such as f _L1 −2f _u and f _L1 −3f _u , which is converted to f _IF1 when receiving the desired channel? However, it will always occur. However, this interference can be removed by adding fixed band pass filters to the input side for each of the VHF low band, UHF high band, and UHF bands.

However, if the first intermediate frequency and mixing method are set as described above, 2f _u -f _L1 will cause interference in the UHF band.
Since this interference is the difference between the second harmonic of the interference signal and the fundamental wave of the local oscillation signal of the first mixer, it causes a large amount of interference.

The following will explain the case of receiving a US TV channel as an example.

If channel 56 (center frequency: 725MHz) is the desired reception channel, the first intermediate frequency is
Since the frequency is 330MHz, the frequency of the local oscillation signal of the first mixer is 1055MHz. When there is a 51 channel signal (video carrier frequency (693.25MHz, audio carrier frequency: 697.75MHz), 51
By mixing the second harmonic of the channel with the local oscillation signal of the first mixer, the second harmonic component of the video carrier of the 51 channels will be present within the first intermediate frequency band of the desired channel. FIG. 3 shows this state. In FIG. 3, 31 is a frequency-converted audio carrier signal of the desired channel (frequency, 327.25MHz), 32
is the frequency-converted video carrier signal (frequency, 331.75MHz) of the desired channel. 33 is
This is an interference signal (frequency, 331.5MHz) caused by the second harmonic of the video carrier wave of channel 51.

Furthermore, if the first intermediate frequency (330MHz) and mixing method are set as described above, 46 channels (center frequency: 665MHz, video carrier frequency: 663.25MHz, audio carrier frequency:
667.75MHz), the second harmonic of the desired channel's own video carrier wave is frequency converted, resulting in the same frequency relationship as shown in Figure 3 and causing interference.

The above disturbances can interfere with UHF TV channel signals.
This always occurs when converting to the first intermediate frequency in the 300 to 400 MHz band, and causes beat disturbance on the TV screen.

Next, the output signal frequency of the first mixer, that is, the first intermediate frequency, is set to 3000MHz, for example, and the mixing method of the first mixer is a combination of the local oscillation signal frequency (f _L1 ) and the received signal frequency (f _R ). Consider the case where the sum is the first intermediate frequency ( _fIF1 ).

With such a mixing method, the difference between the second and third harmonics of the interference signal frequency (f _u ) and the second harmonic of the local oscillation signal frequency, that is, 2f _L1 −2f _u , 2f _L1
-3f _u falls within the first intermediate frequency band of the desired channel.

An explanation will be given below using an example of receiving a US TV channel.

When receiving 50 channels (center frequency, 689MHz), the local oscillation signal frequency of the first mixer is
It becomes 2311MHz. 70 channels (video carrier frequency: 807.25MHz, audio carrier frequency:
811.75MHz), the difference between the second harmonic of the local oscillator signal frequency and the second harmonic of the audio carrier frequency of the 70th channel is 2998.5MHz, and the first of the 50th channel, which is the desired channel, is 2998.5MHz.
It penetrates into the intermediate frequency band and causes interference.

The purpose of the present invention is to solve the above problems.
An object of the present invention is to provide a double super-heterodyne VHF-UHF all-band tuner suitable for TV receivers.

In the present invention, various types of interference that cannot be prevented by conventional methods are removed by selecting an optimal first intermediate frequency and adopting a suitable mixing method. as,
The first mixer is configured as follows. That is,
A first coupled line consisting of a micro-strip line to which a first oscillation signal, which is the output of a first oscillator, is applied to one end and an open end at the other end; A resistor and a capacitor are connected in parallel between a second coupled line consisting of a micro-strip line that is coupled in parallel and has a grounding section approximately at the center thereof, and both open ends of the second coupled line. A first circuit in which the first and second diodes with polarity in the same direction are connected in series, and a third circuit in which a resistor and a capacitor are connected in parallel are connected and installed in series. a low-pass type circuit group consisting of a micro-strip line, one end of which is connected between the connecting portions of the first and second diodes, and the other end of which is connected to the output side of the broadband amplifier. Similarly, one end is connected between the connection portions of the first and second diodes, and the other end is connected to the connection portion of the first and second diodes.
a high-pass type third wave generator consisting of a micro-strip line connected to the input side of the wave generator;
It consists of a single balanced mixer.

By setting the first intermediate frequency and the mixing method as described above, the interference described in the conventional example is eliminated.

Below, we will discuss in detail how these disturbances are removed.

Considering TV signals from channels other than the desired channel as interference signals, the range of the interference signal is
For US TV bands, VHF road band
54~85MHz, VHF high band 174~
216MHz, and the UHF band 470-890MHz should be considered.

In addition, in the case of Japan TV band, VHF low band 90~108MHz, VHF high band 170~
222MHz, and the UHF band 470-770MHz should be considered.

Spurious interference generated in the first mixer, excluding beat interference between channels, consists of the first mixer's local oscillation signal frequency (hereinafter abbreviated as f _L1 ) and the interference signal frequency (hereinafter abbreviated as f _u) . This is because the spurious caused by harmonic mixing with ) enters the band of the first intermediate frequency (hereinafter abbreviated as f _L1 ) of the desired reception channel, and this relational expression is expressed by the following equation.

|mf _L1 ±nf _u |=f _IF1 (m, n: 0, 1, 2,
3.) The harmonics of f _L1 and f _u are considered here up to the third order.

It is meaningless to consider the order beyond that because the system is saturated.

When the above-mentioned interference components are arranged according to the harmonic order of the local oscillation signal frequency f _L1 , the result is as follows.

The second and third harmonics of the interfering signal themselves enter the first intermediate frequency band.

2f _u , 3f _u Fundamental wave of local oscillation signal and secondary of interference signal, 3
Due to mixing with the next harmonic ｜f _L1 ±2f _u ｜, ｜f _L1 ±3f _u ｜ The second harmonic of the local oscillation signal and the fundamental wave, second harmonic, and third harmonic of the interference signal Due to mixing ｜2f _L1 ±f _u ｜, ｜2f _L1 ±2f _u ｜, ｜2f _L1 ±3f _u ｜ 3rd harmonic of local oscillation signal and fundamental wave, 2nd harmonic, 3rd harmonic of interference signal By mixing with |3f _L1 ±f _u |, |3f _L1 ±2f _u |, |3f _L1 ±3f _u | Now, 2700MHz is selected as the first intermediate frequency,
Considering the case of receiving US TV channels, the first
The frequency band of the local oscillation signal of the mixer is 2757~
It becomes 3587MHz.

As mentioned above, the interference signal is 54~
Consider VHF low band, VHF high band, and UHF band within 890MHz.

If 2f _u and 3f _u in the above terms directly fall within the band of the first intermediate frequency of the desired reception channel, this will not occur at all since the interfering signal f _u is in the frequency band.

In the above-mentioned mixing of the fundamental wave of the local oscillation signal and the harmonics of the interference signal, interference occurs in f _L1 −2f _u and f _L1 −3f _u from the frequency bands of the respective signals.

This spurious interference due to harmonics occurs no matter what first intermediate frequency or mixing method is adopted, and it is necessary to suppress the interference signal that generates spurious interference due to harmonics on the input side. Interference in the above terms and terms, that is, mixing the second harmonic or third harmonic of the local oscillation signal of the first mixer with the fundamental wave and harmonics of the interfering signal causes it to enter the first intermediate frequency band of the desired channel. The frequency band of the second harmonic of the local oscillation signal is 5514 to 7174 MHz, the third harmonic thereof is 8271 to 10761 MHz, and the frequency band of the interfering signal is 54 to 890 MHz. Rather, it does not occur at all.

Similarly, if you select 2700MHz as the first intermediate frequency and receive the Japan TV channel, the first
The frequency band of the local oscillation signal of the mixer is 2793~
3467MHz band, and except for beat interference between channels, interference from channels other than the desired channel will be the same as when receiving the US TV band.

Also, since the Japan TV band is in the band from 90 to 770 MHz, the first intermediate frequency is set to, for example,
Even when selecting 2520MHz, when receiving the Japan TV band, interference from channels other than the desired channel will be the same as described above, and the problem is that the fundamental wave of the local oscillation signal of the first mixer and other channels Only mixing with channel harmonics is performed.

Further, according to the present invention, it is possible to provide a VHF-UHF all-band tuner with low noise characteristics and low intermodulation distortion characteristics.

In the preferred embodiment, the noise figure is about 5 dB in the VHF band and about 7 dB in the UHF band, and the tuner input level of adjacent or adjacent channels that causes 1% cross-modulation distortion on the desired received channel is ,
-20 to -25dBm.

In particular, low cross-modulation distortion characteristics are achieved using a low-distortion RF amplifier, a unique diode configuration, and a single balanced mixer.

The detailed structure will be described later, but when the first mixer presented in the present invention generates 1% cross-modulation distortion in the desired reception channel, the adjacent channels or mixer inputs of the adjacent channels are as follows: It is approximately 0dBm.

In addition, by using a fixed frequency band that selectively selects the first intermediate frequency, appropriate settings of the bandwidth of the pass filter, and an amplifier for the second intermediate frequency with a unique circuit configuration, the adjacent channel can be applied to the desired channel. The intermodulation distortion can be made to the same interfering signal level as when adjacent channels are interfering.

Examples according to the present invention will be described in detail below.

FIG. 4 is a block diagram of a VHF-UHF all-band tuner for receiving Japanese TV channels used in the present invention.

The input signal input from the terminal 40 is input to the input filter circuit 41. This filter 41
It includes a trap circuit and a high-pass wave filter to remove intermediate frequency interference signals, FM signals, etc. that interfere with the intermediate frequency of the TV receiver.
It attenuates the intermediate frequency signal of the TV receiver, or the signal in the 1/2 frequency band, by approximately 40 dB. The output of the input filter circuit is input to a variable attenuator 42 composed of a pin diode. The loss in the passband of this variable attenuator is approximately
1dB, approximately 1.5dB in the UHF band, and the maximum attenuation is
It is 50dB in the VHF band and 40dB in the UHF band. The output of the variable attenuator 42 is an RF signal with a two-stage transistor configuration.
The signal is input to an amplifier 43. The gain of an RF amplifier is approximately
21dB, and the noise figure is less than 2.5dB in the VHF band.
It is less than 3.5dB in the UHF band.

The output of the RF amplifier 43 is input to a first input terminal of a first mixer 45 configured with a diode single balanced mixer. mixer 45
The output of a voltage controlled oscillator 47 having a one-stage transistor configuration is amplified to a required level by an amplifier 46 and input to the second input terminal of the oscillator. The voltage controlled oscillator 47 generates a necessary oscillation signal corresponding to a desired TV channel by voltage control.

The amplifier 46 amplifies the oscillation signal to 2.5~
Output +15dBm is obtained over 3.5GHz. 1st
The mixer 45 converts the TV signal input to the first input terminal of the mixer 45 into a predetermined first intermediate frequency of 2520 to 2520 using the oscillation signal of the voltage controlled oscillator 47.
Convert frequency to 2700MHz. Select 2520MHz as the first intermediate frequency that does not cause any interference,
As described above in the mixing method, if the difference between the local oscillation signal frequency of the first mixer, that is, the oscillation signal frequency of the voltage controlled oscillator, and the frequency of the received TV channel signal is set to be the first intermediate frequency, the voltage The required oscillation frequency band of the controlled oscillator is
2613~3287MHz.

The first mixer 45 is a novel mixer proposed by the present invention, and is a diode single-balance type mixer with low noise characteristics and low distortion characteristics. The noise figure of mixer 45 is 7 dB in the VHF band and 7 dB in the UHF band.
The conversion loss when converting the frequency to 2520MHz is 6dB in the VHF band and 7dB in the UHF band. The output of the first mixer 45 is input to a frequency-fixed band pass filter 48 that selects a TV channel signal frequency-converted to a first intermediate frequency of 2520 MHz. The frequency-fixed band pass filter 48 is a coaxial filter,
In order to avoid adjacent channel interference as much as possible in the following circuits, the bandwidth is set to 5MHz. center frequency,
Insertion loss at 2520MHz is approximately 5dB. The output of the fixed band pass filter 48 is input to a first input terminal of a second mixer 49. Second
A second input terminal of the mixer 49 is connected to a fixed oscillator 50.
The output of is input. the first intermediate frequency
When selecting 2520MHz and receiving the Japanese TV channel, the output frequency of the fixed oscillator 50 is:
It becomes 2463MHz.

The second mixer 49 is of the diode single balance type, with a conversion loss of 5 dB and a noise figure of
It is 5dB.

The second mixer 49 converts the first intermediate frequency signal selected by the fixed band pass filter 48 into a second intermediate frequency.

When receiving Japanese TV channels, the frequency is converted to the 57MHz band.

51 was frequency converted by the second mixer 49
This is an intermediate frequency amplifier that amplifies a 57 MHz intermediate frequency signal, has a gain of 15 dB, a noise figure of 2.5 dB, and an adjacent channel level of -20 dBm or more that gives 1% cross-modulation distortion to the desired TV channel. 52 is a fixed band for selectively transmitting the intermediate frequency signal and attenuating the video carrier signal and audio carrier signal components of the upper and lower adjacent channels in order to suppress adjacent channel interference in the intermediate frequency amplifier on the output side.・Pass filter and trap circuit.
The insertion loss at an intermediate frequency of 57MHz is approximately 3dB. Further, the amount of attenuation in the frequency-converted upper adjacent channel video carrier wave 52.75 MHz and lower adjacent channel audio carrier wave 60.25 MHz is approximately 30 dB.

The output of the filter 52 is output to an output-tuned amplifier 5.
3 and amplified to the required level. The gain of amplifier 53 is 20 dB.

The terminals 55, 56, and 57 are an AGC voltage supply terminal, a channel selection voltage supply terminal, and an AFC voltage supply terminal, respectively.

The AGC operation of the tuner of this embodiment is set so that the input level of the desired reception channel in the RF amplifier 43 is always −55 dBm or lower.

Generally, in a double super-heterodyne tuner, it is necessary to apply AFC to the local oscillator of the first mixer, that is, the voltage controlled oscillator, and the local oscillator of the second mixer, that is, the fixed oscillator.

In a preferred embodiment of the present invention, only the voltage controlled oscillator 47 is provided with an AFC terminal by providing a fixed oscillator 50 with good frequency stability against power supply voltage fluctuations or temperature fluctuations.

According to the present invention, the image signal frequency of the first mixer 45 is 5040 MHz higher than the desired reception channel signal frequency, which is twice the first intermediate frequency. In this embodiment, which receives the Japan TV band, the image signal frequency is 5133 to 5807 MHz. Since the first input of the first mixer 45 is connected to the output of the RF amplifier 43, image disturbance of the first mixer 45 is not a problem at all.

The image signal of the second mixer 49 has a frequency lower than the first intermediate frequency by twice the second intermediate frequency. In the case of this method, the only thing that removes this image signal is the fixed band pass filter 48 that selects the first intermediate frequency. Nearby, a fixed band pass filter 48 provides attenuation of 75 to 80 dB, and the suppression characteristic of the image signal generated by the second mixer 49 is 75 to 80 dB.

In the case of this embodiment, the overall noise figure as a tuner is about 5 dB in the VHF band and about 7 dB in the UHF band.

When the level of the desired reception channel is -55 dBm or less and the variable attenuator is not attenuating, which is the most severe situation for tuner interference characteristics, 1% cross-modulation distortion is generated in the second intermediate frequency signal of the desired channel. The input level of adjacent adjacent channels or adjacent channels is −20 to −25 dBm.

Hereinafter, the characteristic individual circuits of the present invention will be explained in detail.

FIG. 5 shows a VHF-
A specific circuit example of the first mixer 45 of the UHF tuner is shown. This mixer is a micro mixer.
A diode with a unique structure using a strip line.
It is a single-balanced mixer, consisting of a micro-strip line fabricated on a dielectric substrate such as a Teflon, fiber, or glass substrate, as well as diodes, resistors, and capacitors.

This mixer is an up converter that converts the TV channel signal from VHF to UHF to a first intermediate frequency of an appropriate frequency between 2520 and 2700 MHz, and is characterized by its small size and low distortion characteristics.

The one shown in Figure 5 is constructed on a Teflon fiber glass substrate, approximately 28 x 25 mm ²
It has an area of 61, 62, 6 in the figure
3 is a signal input terminal, a terminal for taking out the first intermediate frequency signal, and a terminal for inputting a local oscillation signal, each consisting of a 50Ω micro-strip line, and the input signal frequency is 50 to 1000MHz, local oscillation. The signal frequency is 2570-3520MHz.

The line 65 and the lines 66 and 67 constitute a parallel coupled line with an interval of about 0.1 mm.

Almost the center frequency of local oscillation frequency 3000MHz
If the wavelength on the substrate at λ _gL1 is 65 and 6
The electrical length of the parallel connection between lines 6 and 67 is about λ _gL1 /8, and the electrical length of the parallel connection between lines 65 and 66 is about λ _gL1 /40.

The connection point between the lines 66 and 67 is grounded by a grounding line 77. 64 is an open-ended stub with a characteristic impedance of 50Ω and an electrical length of about λ _gL1 /10. Parallel coupled lines 65, 66, 67 and stub 64
and the grounding line 77 form a balun in the local oscillation signal frequency band.

The output lines 68, 69 of the balun include chip resistors 71, 73, chip capacitors 72,
74 is connected. The values of resistors and capacitors are selected to achieve low distortion characteristics without increasing conversion loss. For example, the resistance value is
The capacitor capacity is selected to be 10Ω and 5PF.

70 is a silicon shot barrier diode. 75 and 76 are diplexers for separating input and output signals, and 76 is a low-pass filter for input signals.
Filter 75 is a high pass filter for the output intermediate frequency signal.

This mixer circuit has low noise due to the broadband balance of the uniquely structured balun for local oscillation signals, and by inserting series resistors and series capacitors of appropriate values between the output line of the balun and the diode. Achieves low distortion characteristics.

FIG. 6 shows an example of a specific circuit of the second mixer 49. This mixer is a diode single-balanced mixer with a unique structure using micro-strip lines.
It is characterized by low noise. The basic structure of the present mixer circuit is related to an application filed by the same applicant.
(Japanese Patent Application No. 54-130573) The device shown in FIG. 6 is constructed on a Teflon fiberglass substrate and has an area of approximately 25×25 mm ² .

In the figure, 81, 82, 83 are respectively
These are a signal input terminal composed of a 50Ω micro-strip line, a second intermediate frequency signal output terminal, and a local oscillation signal input terminal.

The input signal is passed through a fixed band pass filter 4.
The first intermediate frequency signal selected by 8 is
The input signal frequency is a suitable frequency between 2520 and 2700 MHz, and in the embodiment of FIG.
It becomes 2520MHz. As the local oscillation signal frequency, a signal having a frequency lower than the input signal frequency by the second intermediate frequency is input so as to obtain the necessary second intermediate frequency. In the case of the embodiment shown in Figure 4, the local oscillation signal frequency is
It is set to 2463MHz.

Line 85 and lines 86 and 87 form a parallel coupled line with a spacing of 0.1 mm.

If the wavelength on the board at a local oscillation signal frequency of 2463 MHz is λ _gL2 , then the electrical length of the parallel connection of lines 85, 86, and 87 is approximately λ _gL2 /10, and the parallel connection between lines 85 and 86 is approximately λ gL2 /10. The electrical length of the joint is
It is approximately λ _gL2 /35. The connection point between the lines 86 and 87 is grounded by a grounding line 93.

Reference numeral 94 denotes a short-circuit line for connecting the line 85 and the line 86 at approximately the midpoint of the line 86.
By providing the short-circuit line 94, the sum component (f _L2 + f _IF1 ) of the local oscillation signal (f _L2 ) generated by the mixer and the input signal, that is, the first intermediate frequency signal (f _IF1 ), is efficiently used. The necessary difference component (f _IF1 − f _L2 ), that is, the conversion loss characteristic for the second intermediate frequency
It is possible to improve the noise figure characteristics.

84 is an open-ended stub with a characteristic impedance of 35Ω and an electrical length of about λ _gL2 /12.

The parallel coupled lines 85, 86, 87, the stub 84, the ground line 93, and the short line 94 form a balun in the local oscillation signal frequency band.

A silicon Schottky barrier diode 90 is connected to the output lines 88, 89 of the balun. 91 and 92 are diplexers for separating input and output signals, and 92 is a band pass filter for input signals.
Filter 91 is a low pass filter for the output intermediate frequency signal.

FIG. 7a shows a specific circuit example of the voltage controlled oscillator 47 and the amplifier 46 for obtaining the first intermediate frequency signal. This oscillator is a voltage controlled oscillator characterized by using an interdigital capacitor in the coupling line between the resonator and the oscillation circuit to achieve coupling that enables oscillation over a wide band and at the same time eliminating the need for coupling adjustment. It is. This oscillator is
TV signals from VHF to UHF can be received with a single oscillator without switching.
Oscillation is possible over a wide band of 1000MHz.

The one shown in FIG. 7a is constructed on a Teflon fiberglass substrate, in which a microstrip line 99 and a varactor diode 100 form a resonator, and an interdigital capacitor 98 connects it to the oscillation circuit. is forming. The resonator is made smaller by bending the microstrip line 99 into a U-shape without deteriorating its characteristics. The oscillation frequency is controlled by the voltage applied to terminal 101. The coupling between the resonator and the oscillation circuit is achieved by using interdigital capacitors to achieve a wide band and no adjustment.
The pattern 97 is a stub for matching the oscillation circuit and the resonator side. L ₇₃ and L ₇₄ are high-frequency chiyoke coils set to approximately λ _gL1 /4, where λ _gL1 is the wavelength on the substrate at 3000 MHz, which is approximately the center of the oscillation frequency, and C ₇₅ to C ₇₇
is a high frequency grounding capacitor. _C74 , _C78 ,
The negative resistance of the oscillator circuit can be controlled by pattern 96, and in the preferred embodiment, _C74 is about 1PF and _C78 is about 5PF.
~10PF.

The amplifier 46 uses a grounded emitter type with two stages of transistors in order to provide high output and sufficient isolation, and its output is taken out from a terminal 95 and inputted to the first mixer 45.

This oscillator uses a voltage controlled oscillator 47 and an amplifier 46 to generate an output over a frequency range of 2500 to 3500MHz.
Obtains an oscillation output of 15dBm.

FIG. 7b is a specific circuit diagram of a circuit that performs AFC by superimposing an AFC voltage on a tuning voltage for receiving a desired channel. A tuning voltage for receiving the desired channel is applied to the terminal 56, an AFC voltage that changes according to the deviation in the oscillation frequency is applied to the terminal 57, and a composite voltage is taken out from the terminal 102 and supplied to the varactor diode to correct the frequency deviation. compensate
This is an AFC circuit. This circuit easily achieves the high frequency stability required for color image reception, and also uses resistor division, which allows current to flow into the power supply side depending on the magnitude relationship of the tuning voltage and AFC voltage.
A feature of this circuit is that it can prevent phenomena that cannot be avoided with AFC circuits.

FIG. 8 shows a specific circuit example of a fixed frequency oscillator 50 for obtaining the second intermediate frequency signal. This oscillator is a fixed frequency oscillator characterized by bending a capacitively mounted shortened half-wavelength resonator into a U-shape to reduce the size of the resonator without deteriorating its characteristics. Further, for coupling between the resonator and the oscillation circuit, magnetic field coupling is employed in which the degree of coupling changes depending on the distance from the apparent shot point at the center of the half-wavelength resonator, thereby simplifying the coupling. Furthermore, this oscillator minimizes frequency fluctuations by making the coupling between the resonator and the oscillation circuit as loose as possible, and by optimally selecting the bias conditions and emitter resistance _R96 .
The frequency is kept within 200 to 300MHz, and a highly stable oscillator with little frequency fluctuation is achieved with a simple configuration.

The one shown in Fig. 8 is constructed on a Teflon fiberglass substrate, and a shortened half-wavelength resonator is constructed with a microstrip line 107 and a fixed capacitor _C95 . The coupling between the resonator and the oscillation circuit is formed using magnetic field coupling that changes depending on the distance from the shoot point. The oscillation output is taken out from the terminal 103 and input to the second mixer 49. L ₉₀ is a chiyoke coil set to approximately λ _gL2 /4, where λ _gL2 is the wavelength on the substrate at an oscillation frequency of 2463 MHz, and C ₉₁ is a high frequency grounding capacitor. C ₉₂ , C ₉₃ , and the pattern 106 can control the negative resistance of the oscillation circuit, and in a preferred embodiment,
_C92 is about 1PF, and _C93 is 10-20PF. The oscillation frequency can be finely tuned using the microstrip line 10.
This is achieved by providing a tuning screw on the top lid at the open end of the 7, and changing the spacing between them.

This oscillator uses a capacitively mounted shortened half-wave resonator made by bending a microstrip line into a U-shape to reduce the size. This is a highly stable oscillator that uses magnetic field coupling that changes depending on the distance from the shot point, and has a small and simple configuration that suppresses frequency fluctuations to within 300KHz.

FIG. 9 shows a specific example of the configuration of the frequency-fixed filter 48 that selects the first intermediate frequency. This filter has three stages of resonators, and the coupling between the stages is made by providing coupling holes in the shield plate.The input and output are the external circuit, take-out terminal, and A configuration with integrated output coupling is used.

The one shown in Figure 9 is 26 (W) x 40 (L) x 14
(H) It has a size of ^mm3 . A resonant circuit consisting of resonators 109 to 111 and tuning screws 108 is constructed in a housing 114, and input and output coupling is performed through a transmission line 115 constructed on a dielectric substrate 116, and at the same time, extraction from the wave generator is performed. Direct connection to the microwave integrated circuit without using a coaxial connector eliminates the mismatch that occurred at the connection part,
Improves characteristic deterioration due to connection. Furthermore, by providing coupling holes 113 in the shielding plate 112 for interstage coupling, the high-order spurious characteristics of the filter are improved and spurious interference caused by harmonic mixing between local oscillators generated in the second mixer is reduced. ing. 117 is a screw for fixing the dielectric substrate to the resonator. This filter improves the in-band characteristics of the desired reception channel and improves the interference rejection characteristics in the circuit after the filter.
The bandwidth is set to 3~5MHz. center frequency
The characteristics of a filter with a bandwidth of 2520MHz and a bandwidth of 5MHz are:
Insertion loss is 5dB, input/output VSWR is less than 1.5, and attenuation of 75 to 80dB is obtained at a center frequency of ±114MHz.

FIG. 10 shows the frequency response 19 of the fixed band pass filter 48 for the first intermediate frequency signal.
0 and the frequency response 191 of the intermediate frequency amplifiers 51 to 53. In the figure, each frequency response indicates the amount of attenuation relative to the center frequency. In the figure, f ₁ and f ₂ indicate frequencies corresponding to frequency responses 190 and 191, respectively. Also, N, N+1,
N-1, N+2, and N-2 respectively indicate a desired reception channel, an upper adjacent channel, a lower adjacent channel, an upper adjacent channel, and a lower adjacent channel.

The fixed filter 48 is set to have a bandwidth of 5 MHz in order to improve the in-band characteristics of the desired reception channel and to prevent interference in subsequent circuits as much as possible. As shown in the figure, the attenuation in adjacent channels is 20 dB or more, and the attenuation for the video carrier signal of the lower adjacent channel and the audio carrier signal of the upper adjacent channel is 15 dB or more. The amount of attenuation for the audio carrier signal and the video carrier signal of the upper adjacent channel is several dB.

Therefore, adjacent channel interference occurs in the circuits after the fixed filter 48, especially in the intermediate frequency amplifiers 51 to 53. In the present invention, the intermediate frequency amplifiers 51 to 53 are provided with a frequency response as shown in FIG. 10 to improve the interference characteristics caused by adjacent channels in the amplifiers.

FIG. 11 shows an intermediate frequency amplifier 51 and a filter 5.
2. It is a wiring diagram of the output side intermediate frequency amplifier 53.
192 and 193 are input and output terminals, respectively. In order to obtain low noise and low distortion characteristics, the intermediate frequency amplifier 51 has R ₁₀₄ ,
C ₁₀₂ , R ₁₀₃ , and C ₁₀₃ are connected.

C ₁₀₃ is a capacitor for intermediate frequency band and grounding.
C ₁₀₂ and R ₁₀₄ are set to appropriate values so as to achieve low distortion characteristics without deteriorating the noise characteristics of the amplifier. In a preferred embodiment, the value of R ₁₀₄ is 10-30Ω
and the value of _C102 is 100-200PF.

The noise figure of the intermediate frequency amplifier 51 is 2.5 dB or less, and the input level of the adjacent channel that gives 1% cross-modulation distortion to the desired reception channel is -20 dBm or more.

The filter 52 basically consists of a 57 MHz band ceramic filter P ₂ and ceramic resonators P ₁ and P ₃ . Ceramic filter P ₂ is a single-pole filter, with the ground electrode connected to
C ₁₀₅ and L ₁₀₂ are added.

Ceramic resonator P ₁ is a trap filter at the lower adjacent channel audio carrier frequency translated to the second intermediate frequency band, ie 60.25 MHz. Ceramic resonator P ₃ similarly carries the image carrier of the upper adjacent channel, i.e.
This is a trap filter at 52 and 75MHz.
The trap attenuation is more than 30dB. The input and output inductances L ₁₀₁ and L ₁₀₃ are for input and output matching.

The intermediate frequency amplifier 53 on the output side is a tuned amplifier having a resonant circuit composed of C ₁₀₉ and L ₁₀₄ on the output side. L ₁₀₅ is inductively coupled to L ₁₀₄ so that the output impedance in the 57MHz band is 75Ω.

The intermediate frequency amplifiers 51 to 53 have a noise figure of 3 dB or less and a signal of 1 to 1 for the desired reception channel due to the low noise and low distortion characteristics of the amplifier 51 in the previous stage and the filter circuit 52.
The input level of adjacent channels, which causes % cross-modulation distortion, is -20 dBm or higher.

FIG. 12 shows a second embodiment of the invention. VHF-UHF all for receiving US TV channels
It is a block diagram of a band tuner. This embodiment further improves two-channel beat interference, second-order harmonic interference, and cross-modulation interference compared to the first embodiment. The same parts as in the embodiment of FIG. 4 are denoted by the same reference numerals, and parts that differ only in the set frequency are denoted by the same reference numerals with a ``''' appended to them.

194 and 195 are VHF input terminals and
This is a UHF input terminal. 196 and 197 are band pass filters for VHF low channel, each having a band of 50 to 90 MHz, 170 to 220 MHz.
VHF Haiti channel band with a band of
It is input to a switching circuit 199 through a pass filter. The switching circuit 199 inputs the signal from either the filter 196 or the filter 197 to the variable attenuator 421 composed of a pin diode according to the control voltage applied to the control terminal 205 according to the desired reception channel. . The insertion loss of filter 196 or 197 and switching circuit 199 is less than 1 dB.
The variable attenuator 421 has the same configuration as the first embodiment, with a loss of 1 dB or less in the passband and a maximum attenuation.
It is 50dB. The output of the variable attenuator 421 is VHF
The signal is input to the band RF amplifier 200. RF amplifier 2
00 is a transistor 1 with a gain of 15 dB and a noise figure of 2.5 dB or less in the band of 50 to 250 MHz.
When generating 1% cross-modulation distortion in the desired receiving channel using the amplifier in the next stage, the input level of the adjacent channel or adjacent channel is approximately -
It is 15dBm.

The output of the VHF band RF amplifier 200 is input to the V-U switching circuit 202 together with the output of the UHF band RF amplifier 201.

Reference numeral 198 denotes a UHF band band pass filter having a band of 450 to 900 MHz, and its output is input to a variable attenuator 422 composed of a pin diode. The loss in the passband of the variable attenuator in the UHF band is less than 1.5 dB, and the maximum attenuation is 45 dB. The output of the variable attenuator 422 is a two-stage transistor configuration.
The signal is input to the VHF band RF amplifier 201. The RF amplifier 201 has a gain of 400 to 1000 MHz.
It has a characteristic of 15 dB and a noise figure of 3.5 dB or less, and the amplifier input level of adjacent or adjacent channels when generating 1% cross-modulation distortion in the desired reception channel is about -15 dBm.

The switching circuit 202 for V-U switching is
Depending on the desired reception channel, a control voltage applied to the control terminal 206 controls the output of either the VHF band RF amplifier 200 or the UHF band RF amplifier 201, which is configured by a diode single balanced mixer. first mixer 45'
input to the first input terminal of.

Similarly to the first embodiment, a voltage controlled oscillator 47' is input to the second input terminal of the mixer 45' after being amplified by an amplifier 46'.

2700MHz as the first intermediate frequency that does not cause any interference when receiving the US TV band
Select the oscillation signal of the voltage controlled oscillator and the receiving TV
When the difference from the frequency of the channel signal is set to be the first intermediate frequency, the voltage controlled oscillator 4
The required oscillation frequency band for 7' is 2757~3587MHz
becomes.

The first mixer 45', the voltage controlled oscillator 47', and the amplifier 46' are almost the same as those in the first embodiment, with the only difference being the set frequencies.

The output of the first mixer 45' is the transistor 1
a first amplifier 203 for the first intermediate frequency in a stage configuration;
is input. The first amplifier 203 is 2700MHz
The gain is 6dB and the noise figure is less than 3.5dB.
The amplifier input level for adjacent and adjacent channels that produces 1% intermodulation distortion in the desired received channel is approximately -8 dBm.

The output of the first amplifier 203 for the first intermediate frequency is input to a coaxial fixed band pass filter 48' having a bandwidth of 5 MHz and a center frequency of 2700 MHz. Insertion loss at the center frequency is approximately 5 dB. The output of the fixed band pass filter 48' is input to a second amplifier 204 for the first intermediate frequency. The second amplifier has a one-stage transistor configuration, and has a gain of 6 dB and a noise figure of 3.0 dB or less at 2700 MHz.

The output of the second amplifier 204 is sent to the second mixer 4
It is input to the first input terminal of 9'. The output of a fixed oscillator 50' having an oscillation frequency of 2655 MHz is input to the second input terminal of the second mixer 49'. Reference numeral 52' designates a fixed band pass filter and trap circuit for the second intermediate frequency of 45 MHz, which has the same configuration as the first embodiment except for the set frequency.

The output of the filter 52' is input to an output tuning type amplifier 53' and amplified to a required level.
The gain of amplifier 53' is 25 dB.

The AGC operation and AFC operation of the tuner of this embodiment are completely the same as those of the first embodiment.

In this embodiment, a first amplifier and a second amplifier with low gain, low distortion, and low noise for the first intermediate frequency band are installed on the input/output side of a fixed band pass filter for the first intermediate frequency. By setting this, the overall noise characteristics of the tuner can be
It has become possible to lower the gain of RF amplifiers. Therefore, the amplification gain of the TV channel signal from the tuner input terminal to the input terminal of the first mixer decreases, resulting in cross-modulation distortion interference and
Third-order mutual distortion interference is improved compared to the first embodiment.

In the case of this example, the overall noise figure as a tuner is approximately 5.5 dB in the VHF band and approximately 7 dB in the UHF band, and the The tuner input level of the channel is -15 to -20 dBm.

In addition, by setting fixed band pass filters for VHF low channel, VHF high channel, and UHF on the input side of the RF amplifier, it is possible to generate second harmonic interference in the desired reception channel and to remove signals from other channels. It is attenuated on the input side of the RF amplifier to improve second harmonic interference characteristics. Furthermore, the two-channel beat interference characteristic in which spurious signals of the sum and difference of frequencies of two other channels other than the desired reception channel drop into the desired reception channel and cause interference is improved.

As mentioned before, in the case of US TV channel reception, 2700MHz is selected as the first intermediate frequency, and the first intermediate frequency is determined by the difference between the local oscillation signal frequency of the first mixer and the signal frequency of the desired reception channel. When the intermediate frequency is obtained, the spurious interference that falls within the band of the first intermediate frequency signal of the desired reception channel is divided into the second and third harmonic interference generated in the RF amplifier and first mixer and the interchannel interference. It's a beat disturbance. In this embodiment, these interference characteristics are improved as much as possible.

Furthermore, according to this embodiment, the image signal generated by the second mixer is
Because it is out of the band of the fixed band pass filter for VHF low channel or VHF high channel, and due to the frequency fixed filter 48',
The suppression characteristic in the VHF band of the image signal generated by the second mixer is 85 dB or more.

As described above, according to the present invention, with low noise,
Double conversion VHF with low distortion characteristics
-Can provide UHF all-band tuner.

Particularly low distortion characteristics are achieved by setting the first intermediate frequency to 2520~
A suitable frequency of 2700 MHz is selected, and the first intermediate frequency is obtained by the difference between the local oscillation signal frequency of the first mixer and the signal frequency of the desired reception channel, and the unique structure according to the present invention This is realized by the first mixer.

[Brief explanation of drawings]

Figure 1 is a block diagram of a conventional VHF electronic tuner, Figure 2 is a block diagram showing the basic configuration of a double superheterodyne all-band tuner, and Figure 3 is a block diagram showing the basic configuration of a double superheterodyne all-band tuner. Explanatory diagram showing that interference signals from other channels are generated within the first intermediate frequency band of the desired reception channel when 330MHz is selected, 4th
The figure is a block diagram of a VHF-UHF tuner used in the present invention, and Fig. 5 is a block diagram of a VHF-UHF tuner used in the present invention.
A wiring diagram showing the specific configuration of the first mixer of the VHF-UHF tuner, FIG. 6 is a wiring diagram showing the specific configuration of the second mixer, and FIG. 7a shows the voltage control of the tuner. A wiring diagram showing the specific configuration of the oscillator, FIG. 7b is a wiring diagram showing the specific configuration of the circuit that controls the voltage controlled oscillator of the same tuner, and FIG. FIG. 9 is a plan view showing a specific configuration of a fixed frequency filter that selects the first intermediate frequency signal of the tuner, and FIG. FIG. 11 is a diagram showing the relationship between the frequency response of a fixed frequency filter and the frequency response of an amplifier for the second intermediate frequency signal; FIG. 11 is a wiring diagram showing the specific configuration of the amplifier for the second intermediate frequency signal of the same tuner; FIG. 12 is a block diagram of a VHF-UHF tuner in another embodiment of the present invention. 41... Input filter circuit, 42... Variable attenuator,
43...RF amplifier, 45...first mixer, 46...
Amplifier, 47... Voltage controlled oscillator, 48... Band
Pass filter, 49...second mixer, 50...fixed oscillator, 51...intermediate frequency amplifier, 52...filter, 53...amplifier.

Claims (1)

[Claims] 1. A wideband attenuator that attenuates the signals of all VHF-UHF reception channels, a wideband amplifier that amplifies the output signal of the wideband attenuator, and a frequency variable first oscillation signal that outputs a first oscillation signal according to the desired channel. oscillator, mixes the output signal of the broadband amplifier and the first oscillation signal that is the output of the first oscillator, and generates a first oscillation signal in the 2520 to 2700 MHz band that has a lower frequency than the first oscillation signal. a first mixer for converting the frequency into an intermediate frequency signal;
a first wave generator with a fixed frequency that selectively band-passes the first intermediate frequency signal that is the output of the mixer; a second oscillator that outputs a second oscillation signal with a fixed frequency; a second wave generator that mixes the output of the first wave generator and a second oscillation signal, which is the output of the second oscillator, and converts the frequency into a second intermediate frequency signal;
The first mixer is a micro-strip, to which a first oscillation signal, which is the output of the first oscillator, is applied to one end and whose other end is open. a first coupled line consisting of a line, a second coupled line consisting of a micro-strip line coupled in parallel to the first coupled line and having a ground portion approximately at the center of the parallel coupled line; A first circuit in which a resistor and a capacitor are connected in parallel between both open ends of the coupled line, a second circuit in which first and second diodes with polarity in the same direction are connected in series, a resistor and a capacitor. One end is connected between the connecting portion of the first and second diodes and a circuit group in which a third circuit in which are connected in parallel is sequentially connected and added in series, and the other end is connected to the output of the broadband amplifier. A low-pass type second wave generator consisting of a micro-strip line connected to the side, one end of which is connected between the connecting portions of the first and second diodes, and the other end of which is connected to the first wave generator. A diode single-balanced mixer made of a microwave integrated circuit and a high-pass type third wave mixer made of a micro-strip line connected to the input side of the mixer. VHF-UHF tuner.