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BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the improvement of a double super tuner suitable
for reception of CATV (Cable Television) broadcast, satellite broadcast,
and HDTV (High Definition Television) broadcast in the UHF (Ultra High
Frequency) band or the like, for example.
2. Description of the Related Art
As is well known in the art, a double super tuner is constructed as shown
in FIG. 1. In FIG. 1, a reference numeral 11 denotes an input terminal
which is supplied with an RF (Radio Frequency) signal obtained by
receiving the broadcast. The RF signal supplied to the input terminal 11
is supplied to a wideband BPF (Band Pass Filter) 12 which permits passage
of signals of entire reception frequency band, amplified by an RF
amplifier circuit 13, and then supplied to a first frequency converter
circuit 14.
The first frequency converter circuit 14 frequency-converts (up-converts)
the input RF signal into a corresponding first intermediate frequency
signal based on a local oscillation signal output from a first local
oscillation circuit 15. As the first frequency converter circuit 14, a
balanced-output type frequency converter circuit is generally used.
Therefore, first intermediate frequency signals are output in a balanced
state from the first frequency converter circuit 14.
The first intermediate frequency signals output in the balanced state from
the first frequency converter circuit 14 are converted into an unbalanced
signal by a balanced-unbalanced conversion transformer 16 and then
supplied to an unbalanced-input type BPF 17 for first intermediate
frequency for effecting the band-pass filtering process for the first
intermediate frequency band. The first intermediate frequency signal
output from the unbalanced-input type BPF 17 for first intermediate
frequency serially passes through a first intermediate frequency amplifier
circuit 18 and BPF 19 for first intermediate frequency which are designed
for the first intermediate frequency band and is then supplied to a second
frequency converter circuit 20.
The second frequency converter circuit 20 converts the input first
intermediate frequency signal into a corresponding second intermediate
frequency signal based on a local oscillation signal output from a second
local oscillation circuit 21. The second intermediate frequency signal
output from the second frequency converter circuit 20 serially passes
through a second BPF 22 for second intermediate frequency and second
intermediate frequency amplifier circuit 23 which are designed for the
second intermediate frequency band and is then derived from an output
terminal 24.
As shown in FIG. 2A, for example, the above double super tuner has an
insertion component 26 such as an air-core coil and various types of
on-surface mounting components 27 which are mounted on a printed circuit
board 25. In this case, the printed circuit board 25 has circuit patterns
25a formed on both surfaces thereof. The insertion component 26 is
inserted from the front surface side of the printed circuit board 25 to
the rear surface side and connected to the circuit pattern 25a on the rear
surface by solder 28 together with the on-surface mounting components 27.
For soldering the circuit pattern 25a and on-surface mounting components 27
formed on the front surface of the printed circuit board 25, a reflow
soldering process is used. Further, as shown in FIG. 2B, the printed
circuit board 25 having various types of insertion components 26 and
on-surface mounting components 27 mounted thereon is set in a shield case
29 and circuit blocks thereof are separated by use of shield plates 29a so
as to attain isolation between the circuit blocks.
It is, however, desirable to improved upon the conventional double super
tuner, to simplify the circuit construction and enhance performance. In an
effort to do so, various studies and developments have been made.
SUMMARY OF THE INVENTION
This invention provides a double super tuner which is suitable for small
size, simple in circuit construction, economical, and has a sophisticated
performance.
Our double super tuner includes a first frequency converting means for
frequency-converting an input high-frequency signal into a first
intermediate frequency signal based on a first local oscillation signal. A
filter bond pass filters first intermediate frequency signal output from
the first frequency converting means to produce the first intermediate
frequency band. A second frequency converting means converts an output
signal of the filter into a second intermediate frequency signal based on
a second local oscillation signal. A dielectric filter is used to provide
the above-described band pass characteristic.
With the above construction, since a dielectric filter is used as the
filter for subjecting the first intermediate frequency signal to the
band-pass filtering process for the first intermediate frequency band, an
attenuation amount required for the band-pass filter for the first
intermediate frequency band can be attained and a stable operation can be
easily attained even with temperature variation and deterioration with
time.
Further, a double super tuner according to this invention comprises first
frequency converting means for frequency-converting an input
high-frequency signal into a first intermediate frequency signal based on
a first local oscillation signal; and second frequency converting means
for converting the first intermediate frequency signal output from the
first frequency converting means into a second intermediate frequency
signal based on a second local oscillation signal. In this case, an active
mixer circuit used for the second frequency converting means and a second
local oscillation signal generating circuit are formed in an integrated
circuit form and a surface acoustic wave resonator is used for the
resonance circuit of the second local oscillation signal generating
circuit.
With the above construction, since the active mixer circuit used for the
second frequency converting means and the second local oscillation signal
generating circuit are formed in an integrated circuit form and the
surface acoustic wave resonator is used for the resonance circuit of the
second local oscillation signal generating circuit, the frequency
stability can be made sufficiently high with respect to variations in
temperature and humidity.
Further, a double super tuner according to this invention comprises first
frequency converting means for frequency-converting an input
high-frequency signal into a first intermediate frequency signal based on
a first local oscillation signal; and second frequency converting means
for converting the first intermediate frequency signal output from the
first frequency converting means into a second intermediate frequency
signal based on a second local oscillation signal. In this case, an active
mixer circuit used for the second frequency converting means and a second
local oscillation signal generating circuit are formed in an integrated
circuit form and a dielectric resonator is used for the resonance circuit
of the second local oscillation signal generating circuit.
With the above construction, since the active mixer circuit used for the
second frequency converting means and the second local oscillation signal
generating circuit are formed in an integrated circuit form and the
dielectric resonator is used for the resonance circuit of the second local
oscillation signal generating circuit, the frequency stability can be made
sufficiently high with respect to variations in temperature and humidity.
A double super tuner according to this invention comprises first frequency
converting means of balanced output type for frequency-converting an input
high-frequency signal into a first intermediate frequency signal based on
a first local oscillation signal; and second frequency converting means
for converting the first intermediate frequency signal output from the
first frequency converting means into a second intermediate frequency
signal based on a second local oscillation signal. In this case, a
variable impedance element is connected to one of the balanced output
terminals of the first frequency converting means.
With the above construction, since the variable impedance element is
connected to one of the balanced output terminals of the first frequency
converting means, the balance adjustment can be effected so that the
unbalanced amounts of the integrated circuit, transformer and peripheral
circuits can be corrected and the distortion characteristic and leakage
characteristic can be improved.
Further, a double super tuner according to this invention comprises first
frequency converting means for frequency-converting an input
high-frequency signal into a first intermediate frequency signal based on
a first local oscillation signal; intermediate frequency processing means
for subjecting the first intermediate frequency signal output from the
first frequency converting means to a process for the first intermediate
frequency band; and second frequency converting means for converting an
output signal of the intermediate frequency processing means into a second
intermediate frequency signal based on a second local oscillation signal.
The intermediate frequency processing means includes a first dielectric
filter supplied with an output of the first frequency converting means;
first intermediate frequency amplifying means supplied with an output of
the first dielectric filter; and a second dielectric filter supplied with
an output of the first intermediate frequency amplifying means; and the
input and output terminals of the intermediate frequency processing means
are disposed on a diagonal line while the first and second dielectric
filters are disposed on a printed circuit board with the first
intermediate frequency amplifying means disposed therebetween.
With the above construction, since the intermediate frequency processing
means includes the first dielectric filter supplied with an output of the
first frequency converting means, the first intermediate frequency
amplifying means supplied with an output of the first dielectric filter,
and the second dielectric filter supplied with an output of the first
intermediate frequency amplifying means and the input and output terminals
of the intermediate frequency processing means are disposed on a diagonal
line while the first and second dielectric filters are disposed on the
printed circuit board with the first intermediate frequency amplifying
means disposed therebetween, then sufficient isolation can be attained
between the input and output.
Further, a double super tuner according to this invention comprises first
frequency converting means for frequency-converting an input
high-frequency signal into a first intermediate frequency signal based on
a first local oscillation signal; and second frequency converting means
for converting the first intermediate frequency signal output from the
first frequency converting means into a second intermediate frequency
signal based on a second local oscillation signal. In this case, an
insertion component and on-surface mounting component are mounted on one
surface of the printed circuit board and an earth pattern is formed on
most part of the other surface of the printed circuit board.
With the above construction, since the insertion component and on-surface
mounting component are mounted on one surface of the printed circuit board
and the earth pattern is formed on most part of the other surface of the
printed circuit board, necessary circuit isolation can be attained even
when the size of the tuner is reduced, spurious disturbance caused by
outputting the frequency of a difference between high-order harmonics of
two local oscillation signals inherent to the double super tuner into the
first intermediate frequency band can be relatively easily suppressed, and
it becomes effective for suppression of leakage and reduction of influence
of the cover.
Further, in a dielectric filter soldering method of this invention for
coating cream solder on a component earth land formed on the printed
circuit board by use of a solder mask and soldering a dielectric filter,
solder resist are set in preset positions on the component earth land.
With the above method, since the solder resists are set in preset positions
on the component earth land, the thickness of the solder can be made
larger than the prior art case by using the solder mask of the same size,
that is, by use of the same amount of solder. Further, since the solder on
the solder resist is scattered in all directions and a space is formed
between the solder resist and the dielectric filter, stress due to
temperature variation and impact can be alleviated. Further, since a gap
can be made between the printed circuit board and the dielectric filter by
using the solder resist, force acting on the solder can be reduced and
cut-off of the solder can be prevented even when the expansion
coefficients of the printed circuit board and the dielectric filter are
different.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are incorporated in and constitute a part
of the specification, illustrate presently preferred embodiments of the
invention and, together with the general description given above and the
detailed description of the preferred embodiments given below, serve to
explain the principles of the invention.
FIG. 1 is a block diagram for illustrating the operation and construction
of a conventional double super tuner;
FIGS. 2A and 2B are respectively a side cross sectional view for
illustrating the mounting state of circuit components on a printed circuit
board when constructing the above tuner and a perspective view showing the
structure for shielding the circuit blocks formed on the printed circuit
board;
FIGS. 3A and 3B are block diagrams for respectively illustrating a first
embodiment of a double super tuner according to this invention and a
modification thereof;
FIGS. 4A and 4B are block diagrams for respectively illustrating a second
embodiment of a double super tuner according to this invention and a
modification thereof;
FIGS. 5A and 5B are diagrams for respectively illustrating the frequency
characteristic of a single dielectric filter and the frequency
characteristic of a dielectric filter in the second embodiment;
FIG. 6 is a block diagram for illustrating a third embodiment of a double
super tuner according to this invention;
FIG. 7 is a block diagram for illustrating a fourth embodiment of a double
super tuner according to this invention;
FIG. 8 is a block diagram for illustrating a fifth embodiment of a double
super tuner according to this invention;
FIG. 9 is a block diagram for illustrating a sixth embodiment of a double
super tuner according to this invention;
FIG. 10 is a block diagram for illustrating a seventh embodiment of a
double super tuner according to this invention;
FIGS. 11A to 11C are a side cross sectional view and perspective views for
illustrating an eighth embodiment of a double super tuner according to
this invention;
FIG. 12 is a plan view for illustrating a ninth embodiment of a double
super tuner according to this invention;
FIGS. 13A and 13B are a perspective view and plan view for illustrating a
tenth embodiment of a double super tuner according to this invention;
FIG. 14 is a side cross sectional view for illustrating an eleventh
embodiment of a double super tuner according to this invention;
FIGS. 15A and 15B are a plan view and side cross sectional view for
illustrating a method of soldering a dielectric filter on a printed
circuit board; and
FIGS. 16A and 16B are a plan view and side cross sectional view for
illustrating a twelfth embodiment of a double super tuner according to
this invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
There will now be described embodiments of this invention with reference to
the accompanying drawings. FIG. 3A shows a first embodiment of this
invention and portions which are the same as those of FIG. 1 are denoted
by the same reference numerals. In the first embodiment, BPFs 17, 19 for
first intermediate frequency are constructed by dielectric filters.
That is, in the conventional case, the BPFs 17, 19 for first intermediate
frequency are constructed by L (coil)/C (capacitor) tuned filters or
helical filters. However, when the L/C tuned filter or helical filter is
used, the value of Q of the circuit cannot be made large and it is
difficult to obtain a sufficiently large amount of attenuation in a
frequency region near the central frequency. Further, after it is mounted
on the tuner, the adjustment therefor is necessary.
On the other hand, if the BPFs 17, 19 for first intermediate frequency are
constructed by dielectric filters, the attenuation amount required for the
band-pass filter for the first intermediate frequency band can be stably
attained even when it becomes necessary to set a high first intermediate
frequency for wideband reception. Further, the stable operation can be
attained even with temperature variation and deterioration with time.
Further, if the first intermediate frequency is set in a frequency band of
600 MHz, it is possible to insert one BPF 30 for first intermediate
frequency band constructed by a dielectric filter between a
balanced-unbalanced converting transformer 16 and a second frequency
converting circuit 20 as shown in FIG. 3B. It becomes possible to make it
unnecessary to adjust the band-pass filter for first intermediate
frequency band.
FIG. 4A shows a second embodiment of this invention and portions which are
the same as those of FIG. 3A are denoted by the same reference numerals.
In the second embodiment, a feed-through capacitor 31 is inserted between
the balanced-unbalanced converting transformer 16 and the BPF 17 for first
intermediate frequency constructed by a dielectric filter and a
feed-through capacitor 32 is inserted between the BPF 17 for first
intermediate frequency and a first intermediate frequency amplifier
circuit 18.
That is, a general dielectric filter has a frequency characteristic as
shown in FIG. 5A and a sufficient amount of attenuation in the
high-frequency band cannot be attained by use of the single dielectric
filter, and particularly, almost no attenuation can be attained in
high-order resonance points in odd numbers. Therefore, there occurs a
problem that the frequency of a difference between high-order harmonics
generated from the first and second local oscillation circuits 15 and 21
is lowered into the second frequency band to easily generate spurious
disturbances.
However, by connecting the feed-through capacitors 31, 32 to the input
terminal and output terminal of the BPF 17 for first intermediate
frequency, the frequency characteristic as shown in FIG. 5B can be
obtained and a sufficiently large amount of attenuation can be attained in
the high-frequency band.
Further, in a case where the BPF 30 for first intermediate frequency band
constructed by a dielectric filter is connected between the
balanced-unbalanced converting transformer 16 and the second frequency
converting circuit 20 as shown in FIG. 3B, the same effect can be attained
by connecting the feed-through capacitors 31, 32 to the input terminal and
output terminal of the BPF 30 as shown in FIG. 4B.
FIG. 6 shows a third embodiment of this invention and portions which are
the same as those of FIG. 3A are denoted by the same reference numerals.
In the third embodiment, a notch filter 33 including a coupling capacitor
C1, tuning inductor L1 and tuning capacitor C2 is inserted between a BPF
30 for first intermediate frequency constructed by a dielectric filter and
a second frequency converting circuit 20. The resonance point of the notch
filter 33 is determined by a parallel circuit of the tuning inductor L1
and tuning capacitor C2.
That is, if only the BPF 30 for first intermediate frequency constructed by
the dielectric filter is inserted between the balanced-unbalanced
converting transformer 16 and the second frequency converting circuit 20
as shown in FIG. 3B, it becomes difficult to attain a sufficiently large
amount of attenuation in the image rejection band of the second frequency
converting circuit 20. Particularly, when only one dielectric filter is
used, it becomes more difficult.
However, if the notch filter 33 is connected to the output terminal of the
BPF 30 for first intermediate frequency as described above, it becomes
easy to attain a sufficiently large amount of attenuation in the image
rejection band of the second frequency converting circuit 20. The notch
filter 33 can also be used for leakage prevention of the first local
oscillation circuit 15. Further, the same effect can be attained if the
notch filter 33 is connected to the input terminal of the BPF 30 for first
intermediate frequency. The coupling capacitor C1 may be replaced by a
coupling inductor.
FIG. 7 shows a fourth embodiment of this invention and portions which are
the same as those of FIG. 3A are denoted by the same reference numerals.
In the fourth embodiment, an RF amplifier circuit 13, first frequency
converting circuit 14 and first local oscillation circuit 15 are formed in
an integrated circuit form and used as a first frequency converting
section 34, and a second frequency converting circuit 20 and second local
oscillation circuit 21 are formed in an integrated circuit form and used
as a second frequency converting section 35. A tuning circuit 36 including
a coil L2, resistor R1 and variable capacitance diode D1 is attached to
the first local oscillation circuit 15 from the exterior, and a tuning
circuit 37 including a coil L3, resistor R2 and variable capacitance diode
D2 is attached to the second local oscillation circuit 21 from the
exterior.
That is, in the conventional case, a diode double balance mixer constructed
by a discrete component is used as the first frequency converting section
34, and a diode mixer or FET (Field Effect Transistor) constructed by a
discrete component is used as the second frequency converting section 35.
For this reason, there occurs a problem that spurious disturbance caused
by outputting the frequency of a difference between high-order harmonics
generated from the first and second local oscillation circuits 15, 21 into
the first intermediate frequency band tends to occur.
However, in this embodiment, since the active type mixers formed in the
integrated circuit form are used as the first and second frequency
converting sections 34, 35, it becomes possible to reduce the leakage
between the first and second local oscillation circuits 15 and 21.
Therefore, spurious disturbance caused by outputting the frequency of a
difference between high-order harmonics generated from the first and
second local oscillation circuits 15, 21 into the firstintermediate
frequency band can be relatively easily suppressed. At the same time, a
reduction in the size and improvement of the performance can be attained.
FIG. 8 shows a fifth embodiment of this invention. In the fifth embodiment,
a surface acoustic wave (SAW) resonator 38 is used as a resonance circuit
used in the second local oscillation circuit 21.
That is, in the conventional case, since an L/C resonance circuit is used
as the resonance circuit of the second local oscillation circuit 21, it is
difficult to attain the sufficiently high frequency-stability with respect
to the temperature variation and humidity variation. However, if the SAW
resonator 38 is used as the resonance circuit used in the second local
oscillation circuit 21, it becomes possible to attain the sufficiently
high frequency-stability with respect to the temperature variation and
humidity variation.
FIG. 9 shows a sixth embodiment of this invention. In the sixth embodiment,
a dielectric resonator 39 is used as a resonance circuit used in the
second local oscillation circuit 21. That is, in the conventional case,
since an L/C resonance circuit is used as the resonance circuit of the
second local oscillation circuit 21, it is difficult to attain the
sufficiently high frequency-stability with respect to the temperature
variation and humidity variation. However, if the dielectric resonator 39
is used as the resonance circuit used in the second local oscillation
circuit 21, it becomes possible to attain the sufficiently high
frequency-stability with respect to the temperature variation and humidity
variation.
FIG. 10 shows a seventh embodiment of this invention. In the seventh
embodiment, a trimmer capacitor 40 is connected as a variable impedance
element to a transmission line 14a for transmitting one of balanced
outputs of the first frequency converting circuit 14 between the first
frequency converting circuit 14 and the balanced-unbalanced converting
transformer 16. That is, as described before, if the first frequency
converting circuit 14 and the balanced-unbalanced converting transformer
16 are simply directly connected in a balanced form, the circuit balance
and physical balance between the first frequency converting circuit 14 and
the balanced-unbalanced converting transformer 16 become insufficient.
Since the balance adjustment can be effected by connecting the trimmer
capacitor 40 to the transmission line 14a for transmitting one of balanced
outputs of the first frequency converting circuit 14, the unbalanced
components of the first frequency converting section 34 formed in the
integrated circuit form, balanced-unbalanced converting transformer 16 and
the peripheral circuits can be corrected, thereby making it possible to
improve the distortion characteristic and leakage characteristic.
FIGS. 11A to 11C show an eighth embodiment of this invention. As shown in
FIG. 11A, a dielectric filter 41 constructing the BPFs 17, 19, 30 for
first intermediate frequency and the like is constructed in a
non-insertion form, an electrode 41a thereof is connected to a circuit
pattern 42a formed on the front surface of a printed circuit board 42 via
solder 43, and an electrode 18a of a first intermediate frequency
amplifying circuit 18 is connected to a circuit pattern 42b formed on the
rear surface of the printed circuit board 42 via solder 43. FIGS. 11B and
11C show the states of the printed circuit board 42 when viewed from the
front side and rear side thereof, respectively.
In the conventional case, since an insertion type BPF is used, it becomes
difficult to attain isolation between the first intermediate frequency
amplifying circuit 18 and the BPF if the first intermediate frequency
amplifying circuit 18 is disposed on the other surface with respect to the
BPF. However, if the non-insertion type dielectric filter 41 is mounted on
the front surface of the printed circuit board 42 and the first
intermediate frequency amplifying circuit 18 is mounted on the rear
surface of the printed circuit board 42, the size can be reduced without
sacrificing isolation between the dielectric filter 41 and the first
intermediate frequency amplifying circuit 18.
FIG. 12 shows a ninth embodiment of this invention. In the ninth
embodiment, two dielectric filters 44, 45 constituting the BPFs 17, 19 for
first intermediate frequency are disposed with a preset distance
therebetween on the front surface of a printed circuit board 42. The
dielectric filters 44, 45 each have three connection electrodes on each
longitudinal side surface, that is, six connection electrodes 44a to 44f,
45a to 45f in total.
In the dielectric filters 44, 45, the connection electrodes 44a, 45a
respectively disposed on the upper left portions thereof are used as input
terminals and the connection electrodes 44f, 45f respectively disposed on
the lower right portions thereof are used as output terminals. That is, in
the dielectric filters 44, 45, the connection electrodes 44a, 45a used as
the input terminals and the connection electrodes 44f, 45f used as the
output terminals are arranged on respective diagonal lines.
Further, a first intermediate frequency amplifying circuit 18 is disposed
in substantially the central position between the dielectric filters 44
and 45 on the rear surface of the printed circuit board 42. A connection
electrode 44f acting as the output terminal of the dielectric filter 44 is
connected to the input electrode 18b of the first intermediate frequency
amplifying circuit 18 via a circuit pattern 42c formed on the rear surface
of the printed circuit board 42, and the output electrode 18c of the first
intermediate frequency amplifying circuit 18 is connected to a connection
electrode 45a acting as the input terminal of the dielectric filter 45 via
a circuit pattern 42d formed on the rear surface of the printed circuit
board 42.
In this case, if a combination circuit of the dielectric filters 44, 45 and
the first intermediate frequency amplifying circuit 18 is regarded as one
intermediate frequency processing circuit for effecting the process of
supplying a first intermediate frequency signal output from the
balanced-unbalanced converting transformer 16 to the second frequency
converting circuit 20, a connection electrode 44a acting as the input
terminal of the intermediate frequency processing circuit and a connection
electrode 45f acting as the output terminal thereof are disposed on a
diagonal line of the intermediate frequency processing circuit.
That is, the input and output terminals of each of the dielectric filters
44, 45 are disposed on the diagonal line thereof, and at the same time,
the input and output terminals of the intermediate frequency processing
circuit constructed by a combination of the dielectric filters 44, 45 and
the first intermediate frequency amplifying circuit 18 are also disposed
on the diagonal line thereof. With this arrangement, sufficient isolation
can be attained between the input and output terminals of the dielectric
filters 44, 45.
FIGS. 13A and 13B show a tenth embodiment of this invention. As shown in
FIG. 13A, an earth pattern 47 having a larger area than the contact area
of a dielectric filter 46 with the printed circuit board 42 is formed on
the front surface of the printed circuit board 42 in a portion in which
the dielectric filter 46 constituting BPFs 17, 19, 30 for first
intermediate frequency is disposed.
The earth pattern 47 is formed to extend towards the side on which a
connection electrode 46a acting as the input terminal of the dielectric
filter 46 is formed so that it may have an area larger than the contact
area of the dielectric filter 46 with the printed circuit board 42. As
shown in FIG. 13B, the earth pattern 47 is cut away in portions
corresponding to connection electrodes 46a, 46f acting as the input and
output terminals of the dielectric filter 46. Thus, the earth pattern 47
can be made large and sufficient isolation can be attained between the
input and output terminals of the dielectric filter 46.
FIG. 14 shows an eleventh embodiment of this invention. In the eleventh
embodiment, for example, an insertion component 48 such as an air-core
coil and various types of on-surface mounting components 49 are connected
to a circuit pattern 42a formed on the front surface of a printed circuit
board 42 via solder 50. An earth pattern 51 is formed on most part of the
rear surface of the printed circuit board 42 except part of signal lines
and power supply lines and the lead portion of the insertion component 48.
With the above arrangement, necessary circuit isolation can be attained
even when the tuner is made small. Further, spurious disturbance caused by
outputting the frequency of a difference between high-order harmonics
which are generated from the first and second local oscillation circuits
15, 21 and inherent to the double super tuner into the first intermediate
frequency band can be relatively easily suppressed, it becomes
significantly effective for suppression of leakage and reduction of
influence of the cover, and the thickness of the tuner can be made
sufficiently small.
Next, the process of soldering the dielectric filter to the printed circuit
board by reflow is explained. In the above dielectric filter, the method
for stable connection in a small area is used, the entire portion except
the connection terminals is made as an earth pattern. Therefore, in the
prior art, a component earth land 53 with which a dielectric filter (not
shown) is made in contact is formed on a printed circuit board 52 as shown
in FIG. 15A, and a dielectric filter is disposed on the component earth
land 53 with a solder mask 54 disposed therebetween and solder is poured
therein. As a result, the dielectric filter 55 is connected to the
component earth land 53 on the printed circuit board 52 via solder 56.
In this case, if the area of the component earth land 53 is S1, the area of
a portion of the solder mask 54 which is cut away in the form of the
component earth land 53 is S1.times.K (K is generally 1.1), and the
thickness of the solder mask 54 is T1, then the thickness T2 of the solder
56 is expressed by the following equation.
T2=S1.times.K.times.T1/S1=T1.times.1.1.
In order to increase the thickness of the solder 56, the area S1.times.K of
the cut-away portion of the solder | | |
