JPS5951617A - Television tuner for broad band reception - Google Patents

Abstract

PURPOSE:To receive a broad band including a CATV band, by adopting a 3- band switching system to an input tuning circuit section having a single tuning parallel resonance circuit. CONSTITUTION:Tuning coils L15, L16 and band changeover switching diodes DS6, DS7 and the like are added in an input tuning circuit section, an LPF of about 600MHz comprising coils L17, L18 and a capacitor C11 is inserted between this input tuning circuit and an IF filter section, and an antenna input signal is applied to the input tuning circuit from an antenna input terminal via an IF filter section and the LPF. Band changeover switching diodes DS1, DS6, DS7 and a DC changeover diode D4 are turned on and DC changeover diodes D1, D2 are cut off at the receiving of a B3 band, a single tuning parallel resonance circuit is formed, and a high band (M3 band) of 220-440MHz is received selectively. M2 band and M1 band are similarly received selectively.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a television tuner for wideband reception that is capable of receiving even the CA TV band.

In the past, the purpose of general TV tuners was to receive standard broadcasts from the antenna, but recently in the United States, there has been a demand for TV tuners that can also receive CATV bands at the same time. ing.

For example, in the United States, the CATV band allocation is based on the general Vl (F band), where there is a mid band between the low channel and the high channel, and channels corresponding to the super band and hyper band in the frequency range even higher than the V II F band. Their total frequency range extends from 5514 Hz to 438 IHz.

<Prior art> Fig. 1 shows a high frequency amplification circuit of a VHFHF borrowing rebit tuner which has been commonly used in the past.
r] is] a high-frequency amplification transistor consisting of dual-age-1 type IMO3FET, DT, -DT3 are tuning variable capacitance diodes, Ds1-Ds3 are band switching switching diodes, D1-D3 are DC switching diodes, CEl ``'''''CEI5 are both grounding capacitors, R9dI'''Rd5 is) k heavy resistor, L
pbLp2 is a peaking coil, R5+ ~ R54i
j:) Ranjisk T1・1 bias resistor, RI)
3 is the drain resistance of the transistor Trl, RT, -R] 3 is a resistor for supplying the tuning voltage, and the resistors RT+ to RT3 are connected to each tuning voltage application terminal.
'f through each of the variable capacitance diodes DTI to DT3.
A tuning voltage vT is applied to. Further, R1 is a diving resistor, R2 is an AGC voltage supply resistor, Cl-C5 and Ll to L.

are the capacitors that make up the IF filter circuit, and Koinope C4 to C6 are coupling capacitors, C7 is a shorting capacitor, C8 to CIO are DC blocking and tuning capacitors, L5
~L12 is a tuning coil.

The above high frequency amplification circuit can be roughly divided into amplification transistor Tr1, coils L1 to L4, and capacitor C1.
~IF fill section consisting of C3 and tuning coil 5~
It consists of an input tuning circuit section consisting of L8, a variable capacitance diode DT+, etc., and a crotch double tuning circuit section consisting of a tuning coil /I/L, ~LI2, a variable capacitance diode DT2 + B73, etc.

First, when receiving the Bl band (VHF low band), the positive power supply 1B1 is applied and the positive power supply '-B2 is not applied, so the band switching switching diode Ds+ ~
Since both DS2 and DS2 are in the cut-off state and there is a hoe, the input tuning circuit section isometrically uses a tuning coil as shown in Figure 2, ~L8 and capacitor C5, Cg and variable capacitance, diode DT+ and other 1~ Ranjisk Trl
A singly tuned parallel resonant circuit is formed from the input capacitance (I SS ) and the stray capacitance Cs, and at this time, the V Ii F low channel is selectively received.

When receiving the 77B2 band (VHF)\I band, the positive power supply "-B2" is applied, and the switch is switched to 7.
D5. .about.Ds3 are both in the ON state, at this time, the human power tuning circuit section is equivalently shown in FIG. A singly tuned parallel resonant circuit is formed from B8, capacitors C1 and Cs, variable capacitance diode DT+, input capacitor C15s, and stray capacitance C'S, and at this time, the VHF high channel is selectively received.

The conventional general TV tuner shown in Fig. 2 is divided into two bands, the B1 band (V HF low band) and the B2 band (V I-IF high band), as shown in section 2. The reception band was switched by controlling the switching of switching diodes DS+ to DS3 in accordance with the reception of the B2 band.

Problems> However, 55
Even if you try to receive the entire frequency range from MHz to 438 MHz with a conventional 2-band switching TV tuner for normal VHF reception, there is a limit to the capacitance change ratio of the variable capacitance diode, so it is difficult to expand the reception range. As a result, various performances (NF characteristics, selectivity characteristics, etc.) deteriorate due to this, and it has been impossible to obtain a practical television tuner for wideband reception.

<Solution Means> The present invention has been made in view of the above points, and employs a 3-band, 4-band system in the manual tuning circuit section and the crotch double tuning circuit section, and is capable of receiving a wide band including the CATV band. This is a TV tuner that can be used.

<Example> 1-iI, I. An example of the present invention will be described with reference to the drawings.

FIG. 4 shows one embodiment of the present invention, in which the same parts as in the subordinate example of FIG. 1 are denoted by the same reference numerals.

Here, when receiving the frequency range from 55 MHz to 440 MHz, 55~]]OMtlz is set to MI
band (low band), 110 to 220 Ml-I
z"fc M2 band (middle band), and further 220 to 440 Ml-T z "tM3 band (/\
It is divided into three bands for reception.

That is, here, first, in the crotch double tuning circuit section, tuning coils 1vLI31LH are inserted in series with the tuning coil /I/L91Lto, and a switching diode DS4 for band switching is inserted when receiving the B3 band.

I) B5 on, switching diode DS2
Turn off 1Ds3 and tune carp/'L13+
Lta and ++J variable capacitance diode DT2 * DT
3, etc., to form a double-tuned circuit, and at this time, the B1 band is received. When receiving the 2nd band, the switching diodes DS2 and DS3 are on, and the 1st notching diode DS6. I) B5 turns off, at this time tuning coil L9, L+o
+ L131LI4 and variable capacitance 11 diode DT
2. A double tuned circuit is formed by DT3 etc., and I
3□ band is received. Furthermore, when receiving the B1 band, the switching diodes DS2 to DSs are both off, and the diode D3 is on, and at this time, the tuning coils /' t, . A double-tuned circuit is formed, and the B and band signals are received.

On the other hand, in the manual tuning circuit section, a tuning coil LI5 e B16 and band switching switching diodes DSs + DSy, etc. are added to the conventional circuit shown in FIG. 1, and this input tuning circuit section and IF filter section Between the capacitor C11 and the coil B17 + L +8, the I-off frequency is approximately 600 MHz.
A low-pass filter is inserted, and an antenna input signal is supplied from the antenna input terminal to the manual tuning circuit section via the IF filter section and the low-pass filter.

0゛・Here, when receiving the B3 band, the switching diode for band switching is 1! DS+, I) S6. D
Sy and DC switching diode D4 are on IJ, D
The diode DI*B2 for converting CL;+J is in a cut-off state, and at this time, the human power tuning circuit section is expressed as shown in FIG.
*B8+1-15+L16+B18 and ii
J transformation diode I) TI, capacitor C5, Cs
, input capacitance C15s + stray capacitance Cs, etc., form a singly tuned parallel resonant circuit, and in this way, 220MHz to 44MHz
The 0 MHz high band (M3 band) is selectively received.

Also, when receiving B2 band, the switching diode D
S+ and diode D2 are in the on state, switching diode DS6+ DSy and diodes D, D4 are in the cut-off state, and the equivalent circuit of the input tuning circuit section is as follows.
The circuit is the same as the conventional example shown in FIG.
A middle band (M2 band) of 0 to 220 M I-1z is selectively received.

Similarly, when receiving Bl band, the diode D! is on, other diodes DSl + DS6 + I) S7
+DJ, 'Sq,, -B4 are in cutoff state,
The 719th valence of the input tuning circuit section (the heat is the same as the circuit shown in FIG. 2, in this case 55~)] OMHz low band (M+ band) is selectively received.

FIG. 6 shows another embodiment of the present invention, and the band switching operation in this embodiment is almost the same as the operation in the embodiment shown in FIG. 4, and will not be described in detail here. Especially when receiving the B3 band, the band switching switching diode DSI + DS6 + DSy, DSs
and the DC switching diode 1"D is turned on, and the diode DI + B2 is in the cutoff state. At this time, the equivalent circuit of the input tuning circuit section is shown as 1" in Fig. 7, and the coil L5 + Ls l LI5+Le6.
L+st induction coil Ls and capacitor C5°Cs,i
iJ transformation 1i'1 diode DT+ Single tuning type parallel -1 (oscillation circuit is formed, as a result 220MHz~
A high band of 440 MHz is received.

Switching diode D when receiving band B2
S+ and diode D2 are on, other diodes DSa, DS7+ DSs+ DI + B4
is in a cut-off state, and at this time, the equivalent circuit of the input tuning circuit section is the same as the circuit shown in FIG. 3, and the middle band is selectively received. Furthermore, during band reception, diode D1 is in the on state and other diodes DS l
, I)ss, DS7e I)sa I I)2
．． B4 is in the cut-off state, and in this case, the equivalent circuit of the manually tuned circuit section is the same as the circuit shown in FIG. 2, and the low band is selectively received.

In this way, in the manually tuned circuit section of the television tuner of the above embodiment, a singly tuned parallel resonant circuit, which is exactly the same as the input tuning circuit section of a conventional TV tuner for receiving VHF borrowing, is formed when receiving the B, band, and B2 bands. , by taking advantage of the feature that the same performance as the conventional one can be obtained, and adding a few circuit configurations to widen the band.
It is possible to receive three bands using a single-tuned parallel resonant circuit with almost the same configuration, and in this case, the B1 band and B2 band can also be received.
The same characteristics as during band reception can be obtained.

<Effects> As described above, according to the TV tuner of the present invention,...
, y The reception range in the tuning circuit section is B, , B2°I4
．． When switching the three Huffs 1'V (separately), the equivalent circuit of 111', H hand, and B2 hand is N', -61'C:'s V IIF.:I; + Since it is not in any way superior to that of Derevichi, which is reliable, various types of reception 4', 'T!l, without any total deterioration Δl-, [3,, broadband acid that expanded in size to the band 11F reception
f rl:: ('Z su/').

4. Explanation in 121 Blood l; if1 Fig. 1 ij: Follow: A (Kanse 1'/I of the high frequency amplification circuit of a general TV tuner, 152 Fig. 171 Rubichi □-Lee) 3. Hand receiver 1711.'4 human power tuning 1111 road section "11111i 11i1;
Figure 3 - 82-band reception in the same circuit 1: Equivalent circuit of the human-tuned circuit section 1, Figure 4 &
:J, TV tuner related to Ki ηi Akira 1゛)jOlh
, Figure 5 is a 9-value circuit diagram of the manually tuned circuit section of the high frequency amplifier circuit in the example. 6 l"41 if, another example of the TV tuner according to the present invention (4'+Vi diagram of the high frequency amplifier circuit of the example li, Fig. 7 is ' of the same song) fh (
For example, ・B 3 band reception 1] manual tuning time; 1'3 part':';'f11111i'l:
(Each is 1'nl.

1' 1: 'l', ', 1-range disc for high frequency amplification, D1'+, I)72 ・-riJ transformation 1d die band, '-L+, '-16...B3 band receiver Tuning coil for Yu, B86.1) S11...Band L7J
Replacement switch 7 tin type A-1.'.

Claims (1)

[Claims] 1. In the high frequency amplifier circuit of a TV tuner for V HF band reception, a tuning coil for B3 band reception including the CAT'V band and switching for band switching is added to the human power tuning circuit section having an l'li tuned parallel resonant circuit. A television tuner for wideband reception characterized by being equipped with a diode.