Telecommunications – Receiver or analog modulated signal frequency converter – Noise or interference elimination
Reexamination Certificate
1999-05-06
2001-10-23
Vo, Nguyen T. (Department: 2682)
Telecommunications
Receiver or analog modulated signal frequency converter
Noise or interference elimination
C455S333000, C455S349000
Reexamination Certificate
active
06308056
ABSTRACT:
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
25
a
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
25
a
on the rear surface by solder
28
together with the on-surface mounting components
27
.
For soldering the circuit pattern
25
a
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
29
a
so as to attain isolation between the circuit blocks.
It is, however, desirable to improved upon the conventional double super tuner, to simplify 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 band pass filters the first intermediate frequency signal output from the first frequency converting means to produce the first intermediate frequency band. A second frequency converting means coverts 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 intermedi
Abe Shuji
Ono Yuji
Tokunaga Takeshi
Yoshida Kazuyoshi
Kabushiki Kaisha Toshiba
Pillsbury & Winthrop LLP
Vo Nguyen T.
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