JPS58179005A - Converter device - Google Patents

Abstract

PURPOSE:To obtain the stable image eliminating capacity over the entire region of receiving frequencies, by providing a preselector stage between an input terminal and a frequency converting part and a band-pass filter comprising an elastic wave device at the output side. CONSTITUTION:The signal supplied to an input terminal 11 is fed to a preselector stage 13 via an amplifier 12. The stage 13 consists of plural tuning circuits using varactor diodes, and this tuning frequency functions to exclude the image frequency with tracking given to the oscillating frequency of a local oscillating circuit 14. The input signal passed through the stage 13 is converted into an intermediate frequency by a mixer 15 and then led out to an output terminal via an amplifier 17, a surface acoustic wave filter 16 and an amplifier 18.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a converter device that receives and converts radio waves in the SHF band, for example, to a predetermined intermediate frequency. The present invention relates to a converter device that improves the ability to reduce leakage of output to input/output terminals of the device and has low noise reception N%.

[Technical background of the invention and its problems]

The frequency of the radio waves arriving at the receiving antenna is Eiho Broadcasting or CAf.
As f-broadcasting becomes more advanced, so-called double super-hetero gain receiving systems with good sensitivity and selectivity are often adopted. This system, especially satellite broadcasting receivers, has a transmitter installed on the ground, and the output of this transmitter is relayed at a stationary station and sent back to the receiver on the ground, so the transmitted radio waves are very far away. Since the incoming radio waves reach the receiver through a distance, the intensity of the incoming radio waves becomes weak.For this reason, when receiving these radio waves and supplying them to the receiver, the UHF
An outdoor unit that converts and amplifies the reception frequency of the UH
The signal is supplied via a converter device comprising an indoor unit that converts the F-band reception frequency to a VHF-band intermediate frequency. In addition, the circuit configuration of the converter that down-converts a high frequency to a low intermediate frequency is such that a semiconductor element that operates with signals from the UHF band to the VHF band is mounted on a dielectric substrate by 11iL, and a micrometer is placed on this substrate. A resonant line is constructed by providing a strip line by means such as vapor deposition, and each circuit block tube! ! Continue.

The basic condition for this type of converter is that, like a general tuner, the signal-to-noise ratio at the output terminal is high, and low-noise reception performance is determined by this K. In addition, it is desirable that the reception frequency range be wide. However, widening the reception frequency range increases the possibility of image frequency interference. Conventionally, this interference has been dealt with by raising the intermediate frequency, so it has rarely been a problem.

Fig. 1 shows a block diagram of the JL unit in this conventional converter device.
This is an input terminal where an incoming signal of [GHz) is received and converted by an outdoor unit (not shown) and input as a UHF band reception frequency. The frequencies of 305CMHz) to 485CMHz, which are the difference from the unit input signal frequency, are summed so that they can be input to the input terminal LK. The received signal input to this input terminal IK is applied to a mixer 3 via an amplifier 2 for suppressing the image frequency. This mixer 3 constitutes a frequency converter 5 together with a local oscillation circuit 4, and converts the received signal of the indoor unit into 130[MEIx
) is again converted into an intermediate frequency signal. This intermediate frequency signal is sent to an output terminal 7 through a band pass filter. The center frequency of these six bandpass filters is 130CMHz''1, and this circuit limits the required bandwidth of the intermediate frequency signal and sends it to the FM demodulator after the output terminal 7, and the required bandwidth F
i27 [MHz].

In the above configuration, almost no countermeasures against image interference have been taken, except for the receiving frequency range (180 [MHz]).
) Since the intermediate frequency is 130 [■h] for K,
This is because there is no room for the image frequency to exist. Therefore, receive frequency instruction manual! l! There is a need for a device that can receive more frequencies in the SHF band. However, in order to widen the reception frequency and satisfy a wide range of conversion functions, it is necessary to reconsider eliminating the image frequency. The select frequency changes by tracking the change in KFi, and a preselector is required to suppress the image frequency.In order to obtain a sufficient image suppression ratio with the subselector, it is necessary to connect KFi in multiple stages. However, when a multi-stage Briselector is configured using varactor diodes, there is a problem in that the filter performance deteriorates due to variations in the varactor diodes and variations in the coupling of resonant elements made of microstrip lines. Ta.

In addition, it is difficult to adjust the waveform of the bandpass filter 60 on the output circuit side that transmits the intermediate frequency, and it is desirable to have a filter means that can limit the band with constant characteristics against fluctuations in the input signal level and wave number over time. .

Ig2 Diagram #i This shows an example of the circuit configuration arrangement in which the converter device having the nine circuit configuration shown in FIG. 1 is specifically arranged on the board surface. This ll [leave.

Frame-shaped housing 80 for input terminal l and output terminal 7Fi shake, etc.
The #IC is electrically insulated from the housing 8 at a predetermined position and is provided therethrough. A double-sided substrate 9 having substantially the same diameter and size as KFi is housed inside this frame-shaped housing B, and resonant elements of various parts are configured by microstrip lines. This double-sided board 9
The amplifier 2, the mixer 31, the local oscillation circuit 4, the bandpass filter 6, etc. are separated by a shield plate.
This shield plate 10 allows each resonant element of the local oscillation circuit 4 to be connected to the amplifier 2, mixer 3, and bandpass filter 6.
This prevents the oscillation force from electrically coupling with other resonant elements such as the like, and from leaking the oscillation force to the input terminal 1 and the output terminal 7.

However, this method of arranging a shield plate for each prong complicates the housing structure, and once the housing structure is determined, there are restrictions on subsequent circuit arrangement. Furthermore, when all the resonant elements are added to improve the performance of one circuit, the unnecessary coupling between the added resonant elements and the resonant elements of the local oscillation circuit 4 cannot be completely suppressed by the shield plate lOK, and the output The terminal 7 has a problem in that the response ratio between the 4-frequency signal and the unnecessary signal is unacceptably mixed.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and it maintains suppression performance such that the suppression ratio of the image frequency band remains constant over the entire band when the reception frequency width of the SHF band is widened. An object of the present invention is to provide a converter device t which can reduce leakage of local oscillation output and has an excellent ability to eliminate unnecessary signals.

[Summary of the invention]

In order to solve the above problem, the present invention requires an incoming signal! ! an input terminal for inputting a signal that is received and converted into a predetermined frequency band according to the input signal, and converts the reception frequency sent from the input terminal to a predetermined intermediate frequency;
provided in an input circuit section between the input terminal and the conversion section,
It is composed of an elastic wave device provided in a pre-selector stage whose tuning frequency changes by tracking the local oscillation frequency of this conversion section, and an output circuit section which limits the band and sends out the mourning intermediate frequency signal converted by the conversion section. Based on the configuration of , the performance is further improved by using an image-reject type mixer that has attenuation characteristics in the image band of the local oscillation frequency in the conversion section. Not only can you measure the local oscillation frequency into this mixer, but you can further increase the Therefore, by adopting this configuration, a part of the image suppression ratio is obtained in the briselector stage, and furthermore, the image suppression ratio is supplemented in the mixer of the conversion section to increase the briselector stage sum. By configuring the local oscillation circuit on the opposite side of the board from other circuits, it is possible to avoid image disturbance without imposing an unreasonable suppression ratio. This further improves the low noise reception performance of the entire device.

[Embodiments of the invention]

Hereinafter, the present invention will be explained in detail with reference to the drawings from FIG. 3 onwards. First, FIG. 3 shows an embodiment of the present invention, the basic configuration of which is converted into a plotter. In this figure, the reception frequency of the UHF band is received and converted by the input terminal 11KFi outdoor unit (first switching section). This incoming signal is input to the pre-selector stage 13 via the first amplifier 12. As will be described later, this preselector stage 13 #i is composed of a double-tuned circuit using varactor diodes, and its tuned frequency tracks the oscillation frequency of their local oscillation circuit 14 to eliminate image frequencies. have. In order to eliminate this image frequency, if you connect a double-tuned circuit in multiple stages in this briselector stage 13, you can set it to around 40 [dB], which is effective for suppressing the image frequency, and eliminate image interference. However, according to this method, as mentioned above, due to variations in varactor diodes, etc., in practice, the preferable rejection capability t14) cannot be achieved.According to the present invention, the preselector stage The suppression ratio at 13 is kept at a certain constant ratio, and the mixer 15 which controls the conversion section at the next stage suppresses that amount. That is, the output of the preselector stage 13 is supplied to the mixer 15, which can be constructed of an image reject type mixer with a large attenuation amount in the image band. If this configuration is adopted, the image suppression ratio can be further increased by increasing the image suppression ratio. This mixer 15
The oscillation frequency of the local oscillation circuit 14 is injected into , and a frequency that is, for example, a difference from the output frequency of the preselector 13 appears at the output end of the mixer 15 . The frequency of this difference is an intermediate frequency, which is output as an FM signal with a predetermined bandwidth, which is returned to a baseband signal by an FM demodulator etc. after the output terminal, and #i%RF modulation by one device! -, the AM signal is converted into a sum that can be received on the VHF channel of a general television receiver.

Furthermore, in the present invention, a surface acoustic wave filter 16 is provided in an output circuit section that sends out the intermediate frequency signal converted by the mixer 15. This surface acoustic wave filter 16Fi has second filters on its input and output sides, respectively. Since it is equipped with a third amplifier 17 and 18 and is guided to the output terminal 19, it is possible to eliminate variations in the output waveform due to fluctuations in reception frequency and differences in signal level K, and also eliminates the need for waveform adjustment due to its nature. It is.

The specific circuit example shown in FIG. 4 is a configuration of the above basic block diagram using specific circuit elements. In this figure, portions corresponding to each circuit block in FIG. 3 are enclosed by broken lines and given the same reference numerals. First, amplifier 12ti
) Two amplification stages composed of transistors QX and Qx are capacitively coupled, and one input terminal 11 and the first stage transistor Q
1 through a microstrip line Sl (hereinafter referred to as a strip line) #c, and further 1 first stage transistor Q
I and the edge stage transistor Q are coupled by a strip line. Also, each transistor Ql() input, Qs
, In the crotch of Qt is the stub SL of the IJ knob,
Sg is configured, and the frequency characteristics of each amplification stage are determined. Further, an outdoor unit power supply terminal 12-1 is connected between the input terminal 11 and the input side of the first stage amplification transistor Q1 via an inductance L1. This power supply terminal 12-I
When receiving K#iS HF broadcasting, a predetermined voltage is applied so that an incoming signal in the SHF band can be supplied to the amplifier 12. Further, each transistor (h, Q) of the amplifier 12 is configured so that a power supply voltage is applied from a power supply terminal 12-2.

Next, the received signal amplified by the amplifier 12 is guided to a preselector stage 13 forming a double tuning circuit. This briselector stage 13/Ii is a 2-stage briselector that is normally used in 1 stage! One end of the first and second Oka tuning elements L4-Ls formed by a strip line is grounded, and the other end is connected to a varactor diode 41*VDll.
KIM is tied. Each varactor diode VD1
．． The cathodes of VDx are connected to the tuning voltage supply terminal 13-1 through resistors R1s and R1, respectively, and are grounded through capacitors C1 and Cs, respectively. Also, 1st.
211th itliili bulge La, other end K1 of Lm
-4 variable capacitors vcmoves are connected respectively to enable fine tuning of the tuning frequency. 1 more 1st
fji tuning element La K Fi Third tuning element L6 on the input side
is coupled, and the second tuning element R, K i! A fourth tuning element L7 is coupled on the output side. Each third. Fourth tuning element L@.

One end of Lγ is grounded and the other y! The third tuning element L- of each IAFi takes in the output of the amplifier 12, and the fourth tuning element L7 outputs an output signal in a selected band to the image-reject mixer 15 at the next stage.

Further, the varactor diode VDI of the selector stage 13
, the tuning voltage applied to vDw is the local oscillator circuit 14
It is designed so that it is also supplied to K. This local oscillation circuit 1
Reference numeral 4 includes an oscillating section 141 constituted by an oscillating transistor Q3 and a resonating section 14b, which are coupled to each section #i. A first line formed by a strip line in this capacitive coupling part
JIE2 resonant elements RI, L- are coupled, and local oscillation output #i.

The mixer 15 is guided from the second resonant element L9. Further, a varactor diode VDs is provided in series with the first resonant element Ls, and the tuning voltage is applied to the varactor diode VDsK via the first resonant element Ls. Thus, the tuning frequency of the preselector stage 13 tracks the resonant frequency of the resonant section 14b of the local oscillation circuit 14. In other words, when the local oscillation frequency changes in response to a change in the reception frequency, the tuning frequency of the pre-selector stage 13 follows the corresponding input signal wavenumber band and suppresses the image family wavenumber. Note that the oscillation unit 14a [#
'i The power supply voltage of the power supply terminal 12-2 is supplied.

Subsequently, the received output of the pre-selector stage 13 and the local oscillation output of the local oscillation circuit 14 are injected into the image reject type mixer 15 as described above, and the local oscillation output is subjected to heterodyne detection. This mixer 15 is a mixer diode])
xa, Dlb and inductance LWsLll @ Lua
tLub* It has a configuration in which a circuit consisting of capacitors Csa and Csb is connected in cascade.

The mixer 15#i image frequency band, that is, 130 [M
Hz) as the intermediate frequency, and in the case of the upper heterodyne system, the attenuation is set to be maximum near the upper side of 260 [■h], where the image interference is strongest, and image frequency suppression is performed. . Since the image frequency suppression ratio in the pre-selector stage 13 is compensated for by the mixer 15, there is no need to connect double-tuned circuits for eliminating image frequencies in multiple stages. According to experiments, if the double-tuned circuit for the briss selector is combined in two stages, that is, the briss selector used in a single stage is combined in four stages,
Combined with the suppression ability of the mixer 15, sufficient image interference elimination performance was obtained. In this case, H
A suppression ratio of 30 [dB] is achieved, and the mixer 15 achieves a suppression ratio of 15 (dB).
) to compensate for the suppression ratio, so the total was 45.
(dB) or higher suppression ratio can be obtained. This performance is sufficiently satisfactory in terms of image interference elimination ability.

Next, the output of the mixer 15Fi is configured with a transistor Q4 and is led out to the request 2 amplifier 17.

This second amplifier 17a is provided on the input side of the surface acoustic wave filter 16 at the next stage, so that the signal input to the surface acoustic wave filter 16 is converted into an acoustic wave without distortion and filtered.

Further, a third amplifier 18 is also provided at the output @ of the first surface acoustic wave filter 16 to derive an output terminal IQK intermediate frequency signal. The third amplifier 18 is composed of capacitively coupled two-stage amplification transistors Qs e Q#K.

Each second. Third amplifier 17°18KFi power supply terminal 17-1
power supply voltage is applied. With this configuration, a characteristic adjustment section as a filter circuit is not required, and the properties of the surface acoustic wave filter element can be fully exhibited.

The operation of the converter device with the above configuration is as follows.
do. Input circuit section Kll of this converter device! lit
When an incoming signal from one satellite arrives on the receiving air, the outdoor unit converts it to a UHFWO receiving frequency. In this case, the number of local oscillations jl#IL of the outdoor unit (not shown) is fixed, for example, if the incoming mma is 11
．． 10 if it is in the range of 7 (nod 1) to 12.1 [GHz]
．． It is down-converted at a constant frequency of 74 [GHz]. by this.

Input terminal lIK input receiving frequency range #1960[M
Hx ] ~ 1360 [huh]. This reception frequency t
If the signal is directly input to the mixer 15 without passing through the preselector stage 13, the oscillation frequency of the local oscillation circuit 14 will be K 10900 to obtain an intermediate frequency of 130 Ch/Iiz).
Since it changes in the range of 1Hz to 1490MHz,
For example, when receiving 96G[ME(z), the local oscillation frequency will be 1090[MHz]l) 1220CkllHx
]There is an image frequency nearby. A ninth way to eliminate this is to change the tuning frequency of the preselector stage 13 in response to the change in the local oscillation frequency, thereby suppressing the frequency band near the image frequency before injecting the mixed Ill SK. The tuning frequency and bandwidth of the double-tuned circuit of this selector stage 13 are set so as to suppress the image frequency in a band of about 50 (MHz) with the center frequency as the center frequency. Therefore, if multiple double-tuned circuits are connected in the preselector stage 13, a large amount of image attenuation can be obtained and interference can be completely eliminated, but for the reasons mentioned above, the image frequency can only be eliminated using the preselector. Then it was difficult to melt. In the present invention, the image frequency that cannot be suppressed by the preselector stage 13 is further suppressed by suppressing the suppression to about Fiao [dB] at the preselector stage 13, and by configuring the mixer 15 in an image reject type instead. The mixer 15 attenuates the signal by about 15 [dB]. As a result, the overall device Fi4
It was possible to obtain an image suppression ratio of 5()B] or higher.

Thus, the received signal with the image frequency suppressed is mixed 8
15, the signal is converted to an intermediate frequency, and is outputted to an output terminal 19 via a surface acoustic wave filter 16 or the like having good band passability. The intermediate frequency signal led out to the output terminal 19 has a signal waveform with a bandwidth of 27 (MHz), and becomes an AM modulated wave in the VkIF band from the output end of the indoor unit, and is received on the VHF channel.

Next, the mounting aspects of the Compa-jl device constructed as shown in FIGS. 3 and 4 will be explained with reference to FIGS. 555 to 555. FIG. 5 is a one-way configuration diagram of the converter device according to the present invention. Moreover, FIG. 6 is a circuit configuration diagram from the rear side of FIG. 5. Further, FIG. 7 shows a comparison graph with a conventional device showing that the oscillation output leakage of the local oscillation circuit 14 can be improved by adopting the configurations shown in FIGS. 5 and 6.

In FIG. 5, the input terminal 11 and the output terminal 19 are connected to a conductor 21, 21, which passes through the outer frame-shaped casing 200 at a predetermined position.
B and are connected to each other.

Each of the input/output terminals 11 and 19 is connected to a circuit board 220 and a circuit pattern line EMIN on one double side 111 housed in the frame-shaped housing 20, and each circuit terminal, that is, the first amplifier 12
．． Bri selector stage 13. mixture! 15. Local oscillation circuit 14
．． Second. A third amplifier 17, 18 and a surface acoustic wave filter 16 are interposed. Each circuit is divided and arranged in blocks on the dielectric substrate 22 as shown in the figure. More specifically, the first amplifier 12 . An input circuit section 23 consisting of a pre-selector stage 13 is disposed on the left side of FIG. 5, and an output circuit section 24 consisting of a second and third amplifier 17, 18 and a surface acoustic wave filter 16 is disposed on the right side of FIG. ing. The intermediate portion between the input circuit section 23 and the output circuit section 24 is occupied by the π mixer 15. In addition, as shown in FIG. At @, a ground pattern 26 is deposited except for the local oscillation lead-out terminal 14'.In contrast, a ground pattern 27 is deposited on the back surfaces of the input circuit section 23 and output circuit section 24.In addition, the local oscillation circuit It is connected to the input circuit section 23 and the mixer 15 by the back front ground pattern 26#i shield plate 28 of 14.qh The converter device of the present invention has a housing configuration as shown in FIGS. 5 and 6. By doing so, the local oscillation circuit 14 can be installed without providing a conventional shield plate that further divides the frame-shaped housing 20 and also installs a groove in the substrate 22.
It becomes possible to avoid resonant coupling between the circuit block and other circuit blocks. In addition, especially the tuning element group of the preselector stage 13 and the resonant section 1 of the local oscillation circuit 14, where resonance coupling is a problem.
Since the circuits are configured on the front and back sides of the board 220, the degree of coupling with 4b can be reduced.K, since the back side of the selector stage 13 is the ground pattern 27, reliable grounding can be achieved. It is something. In addition, since the input/output terminals 11.19#i are on the opposite side of the local oscillation circuit 14 across the board 2z, leakage of the local IN1 oscillation output to each terminal 11.19 is suppressed.

Figure jI7 shows a graph in which the vertical axis shows the leakage component attenuation ratio of the local oscillation output when the circuit is configured as described above, and the local oscillation frequency is shown on the horizontal axis. , 1 so 29 indicate the *** value according to this configuration. In this figure, an improvement of 10 (dB) Ii degrees can be seen in the variable range of the local oscillation frequency.

In the above description, an image-reject type mixer is used as the mixer 15, but the mixer 15 can be replaced with a normal mixer.

An example of the circuit configuration in this case is shown in FIG.
In the figure, input terminal 81H is connected to pre-selector stage 13, and input terminal 82#- is connected to local oscillation circuit 14, respectively. Both terminals 81 and 82 are connected in common to the cand of diode D1. A resonant circuit consisting of an inductance Lw and a capacitor 'V''CI is connected to the anode side KFI pair of this diode D1, and the connection point between this diode D1 and the resonant circuit is supplied to the amplifier 17 via an output terminal 83. It looks like it will be done.

Therefore, this mixer uses briseleta! The output of the local oscillation circuit 14 is supplied to R1 and mixed, and the difference signal between the two signals is supplied to the amplifier 17. Even if this mixer has a 150-circuit configuration, the KFi performance is inferior to that of a mixer with an image-reject type circuit configuration, but the performance of Sugihen, which is acceptable in practice, can be obtained.The image-reject type mixer has a higher performance. It is also possible to use it differently, such as applying it to things that are

〔Effect of the invention〕

As explained above, according to the present invention, a pre-selector stage that tracks the local oscillation frequency and changes the tuning frequency is provided on the input circuit side of the mixer that completely mixes the received frequency and the local oscillation frequency and converts it to an intermediate frequency. By providing a bandpass filter composed of an acoustic wave device on the output side of the mixer in conjunction with this pre-selector stage, it is effective to obtain stable image rejection capability over the entire receiving frequency range. .

In addition, due to the structure of the board, this 9-wire tatata stage is placed on the side opposite to the component surface of the local oscillation circuit, and a ground pattern is provided on the back side of each component surface to ensure grounding of tuning elements, etc. With this configuration, the degree of unnecessary coupling of the local oscillator circuit with each circuit and the same wI4 element of the K filter selector stage can be reduced without complicated interposition of a shield plate. Moreover, when an image reject type circuit configuration is adopted for the mixer, it becomes possible to further improve the image rejection ability.

This makes it possible to reduce leakage of one local oscillation output to the input/output terminals, thereby providing a converter device f with further improved low-noise reception performance.

[Brief explanation of the drawing]

Figure 1 is a circuit plotter diagram showing a conventional converter device.
Figure 2 is number 15! FIG. 3d is a circuit block diagram of a converter device according to the present invention, and FIG. 4 is a circuit diagram showing a specific example of the circuit shown in FIG. 3. figure. Fig. 5 &li An enclosure configuration diagram when the circuit of Fig. 3 or Fig. 4 is mounted on a board, building 6a! 1 is a circuit configuration diagram of Figure 5 viewed from the back, Figures 7 & 1tt A graph showing an actual measurement example in which the leakage of local oscillation output is improved when the i-path configuration of Figure 5 is applied, Figure 8 d This invention FIG. 2 is a circuit diagram showing another circuit configuration of the mixer that constitutes the mixer. 11...-input terminal, 12, 17.18--amplifier, 13--briselector stage, 14--local oscillation circuit, 15--mixer, 16---elastic surface wave filter, 19... Output terminal, 22... Dielectric substrate, 23... Input circuit section, 24... Output circuit section, 25゜28... Seal)' [, 26, 27...
-・Earth pattern, Q1~Q6...Transistor, L41 Ll + Ll #Lγ・−Tuning element, Ll, Ll−・・Resonant element, ■1~■h・−Varactor diode.

Claims (1)

[Scope of Claims] +11 A conversion section comprising a local oscillation circuit and a mixer that converts the received signal entering the input end into a predetermined intermediate frequency, and conversion between the input end and the conversion section. A preselector stage that changes the tuning frequency by tracking the local excavated frequency 1yvc of the conversion section, and an output circuit that limits the band of the intermediate frequency signal that is the output of the conversion section and sends it to the output end. 1. A converter device comprising: a bandpass filter provided on the side and constituted by an elastic wave device. (2) The converter device according to claim 1, wherein the converter uses an image reject type mixer having four attenuation characteristics in the image band. (3) The input circuit and output circuit of the converter and the mixer are formed on four sides of a dielectric substrate, and the local oscillation circuit is formed on the other side. Converter device according to item 2.