JPS62107529A - Electronic tuner incorporating fixed frequency divider having band changeover function - Google Patents

Abstract

PURPOSE:To simplify the connection between an electronic tuner and an external circuit by incorporating a circuit which counts a signal frequency as soon as a frequency division signal of a fixed frequency divider is outputted and outputs a reception frequency band switching signal in response to the said count into the electronic tuner. CONSTITUTION:The reception is enabled by biasing band pass filters 2, 4 and a VCO6 to a prescribed tuning voltage with respect to a desired reception RF signal fed to an RF signal input terminal 1, the RF signal via the band pass filter 2, an amplifier 3 and the band pass filter 4 is frequency-converted by using a signal of the VCO6 into an IF signal, which is outputted at an output terminal 8 via an IF amplifier 7. A voltage fed to a tuning voltage terminal 11 controls the VCO6 that its output is frequency-divided by a fixed frequency divider 9 and then inputted to a PLL circuit. In this case, the fixed frequency divider 9 counts a signal being the frequency division of the oscillated signal of the VCO6 and outputs a reception frequency band switching voltage. The voltage is fed to the band pass filters 2, 4 and the tuning circuit of the VCO to select the reception band.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an electronic tuner that receives high frequency signals such as television signals, and particularly to an electronic tuner suitable for channel selection using a PLL circuit.

[Background of the invention]

Conventional electronic tuners that receive high-frequency signals such as television signals through multiple reception bands perform channel selection using a PLL circuit, as described in Japanese Patent Application Laid-Open No. 56-11447, the reception frequency band switching signal is determined by a signal from a control unit. This is obtained by driving a voltage generating circuit, and therefore, there is a drawback that one or more signal lines are required in addition to the signal line for setting the frequency of the voltage controlled oscillator for switching the receiving frequency band. Furthermore, in Japanese Patent Application Laid-open No. 57-89153, a tuning voltage for frequency setting of a voltage controlled oscillator is used to compare the base 8% voltage set for each receiving frequency band and output a receiving frequency band switching signal. Although the number of signal lines can be reduced, it is difficult to synchronize with the receiving channel because the switching voltage is generated using a voltage. Especially when the sensitivity of the oscillation frequency to the tuning voltage is high, accurate band switching is difficult. There are drawbacks that make it difficult.

[Purpose of the invention]

The purpose of the present invention is to reduce the number of signal line connections between an electronic tuner having a plurality of reception frequency band switching functions and an external circuit, thereby facilitating the connection, and at the same time ensuring compatibility between electronic tuners having different numbers of reception frequency bands. Furthermore, it is an object of the present invention to provide an electronic tuner that accurately generates the switching frequency according to the receiving frequency band.

[Summary of the invention]

Since the divided output of the fixed frequency divider built into the electronic tuner section has a relatively low frequency, it is relatively easy to count this frequency and generate a reception frequency band switching voltage according to the counted value. Therefore, these switching voltage generation circuits are built into a tuner or a fixed frequency divider IC.

[Embodiments of the invention]

The present invention will be explained in detail below. Figure 1 shows singles-
FIG. 2 is a circuit block diagram when the present invention is implemented in a perheterodyne electronic tuner. 1 is a high frequency signal (RF multiplied signal input terminal).

2 is a variable band pass filter, 3 is an amplifier, 4 is a variable band pass filter, 5 is a mixer, 6 is a voltage controlled oscillator (
VCO), 7 is an IF amplifier.

8 is an IF output terminal, 9 is a fixed frequency divider, 10 is an AGC voltage terminal, 11 is a tuning voltage terminal, and 12 is a frequency division output terminal. For the desired received RF signal supplied to the RF signal input terminal 1, bandpass filters 2 and 4. The VCo 6 is biased to a predetermined tuning voltage to enable reception, and the bandpass filter 2. Amplifier 3. The signal is frequency-converted by the RF multiplied signal VCo6 through the bandpass filter 4 to become an IF signal, which is output to the output terminal 8 through the IF amplifier 7. The voltage supplied to the tuning voltage terminal 11 is a voltage that is input to the PLL circuit after frequency-dividing the VCo 6 by the fixed frequency divider 9, and is supplied from the PLL circuit.

At this time, the fixed frequency divider 9 counts the frequency-divided signal 3 of the oscillation signal of the VCo 6 and outputs a receiving frequency band switching voltage according to the counted value, and this voltage It is supplied to the filter 2.4 and the vCO tuning circuit to select the receiving band.

An example of the basic configuration of the tuning circuit of the bandpass filter 2.4 and the VCo 6 is shown in FIG. 2. 013 and 13' are RF multiplied signal input or output terminals, respectively.
15.25.26.27 are high frequency bypass capacitors,
16 is the first coil, 18 is the second coil, 17Fi
, switching diode.

20 is a varactor diode, 19 is a capacitor, 23 and 24 are resistors, 21 is a first band voltage terminal, 22 is a second band voltage terminal, and 28 is a tuning voltage terminal. This tuning circuit is for receiving two reception bands, the first and second, and receives wc2 or the first reception frequency band by making the switching diode 17 conductive or non-conducting, and receives the reception frequency band by the tuning voltage. Determine the frequency.

The third is another embodiment of the present invention, which is a circuit diagram in which the present invention is applied to a double superheterodyne system. 29 is an RF signal input terminal, 30 is a band pass filter, 31 is an amplifier, 52 is a first mixer, 33
is a VCo, 34 is a bandpass filter, and 35 is the first IF.
36 is a second mixer, 37 is a fixed oscillator, 38 is an IF amplifier, and 39 is an IF output terminal.

40 is a third mixer, 41 is a fixed frequency divider, 42 is a frequency division output terminal, 4 is a band voltage terminal, 43 is a tuning voltage terminal, 4
4 is an AGC voltage terminal. A bandpass filter 30 that divides the RF multiplied signal from the RF signal input terminal 29 into a plurality of reception bands. The frequency is converted by VCO in the first mixer via the amplifier 31, and the RF multiplied signal is also converted into the first mixer with a higher frequency.
The signal becomes an IF signal, is band-limited by a bandpass filter 34, is amplified by an amplifier 35, and then frequency-converted into a normal IP signal by a signal from a fixed oscillator in a second mixer.
After being amplified by the amplifier 58, it is output from the IF signal output terminal 39. vCO is a tuning voltage created by a PLL circuit provided outside the electronic tuner using a signal obtained by dividing the signal of the difference between the oscillation frequencies of VCOsx created by the third mixer 40 and the fixed oscillator 37 by the fixed frequency divider 41. controlled by At this time, the fixed frequency divider 41 counts the signal obtained by dividing the frequency of the VCO, and outputs a band voltage to be set in the reception band according to the counted value. 1 of the filters 50 is selectively operated.The bandpass filter 30 in this case may have a configuration example as shown in FIG.

In Fig. 4, the receiving band is divided into three parts, and one band pass filter is selected and operated by switching with a switching diode, 45 and 46 are RF signal input or output terminals, 47.48° and 49 are the first and second band pass filters. ．． Second. a third bandpass filter; 50 is a switching diode;
51.55.54 is resistance.

52 is a high frequency bypass capacitor, 55.56.57
is the first. Second. This is the third band voltage terminal. 55°56
．． The voltage from the band voltage terminal 42' in FIG. 3 is applied to one of the band voltage terminals 57, and the switching diode that operates the band pass filter corresponding to the reception frequency band becomes conductive. At this time, all other switching diodes become non-conductive.

Figure 5 shows the first fixed frequency divider in Figures 1 and 6.
This is a configuration example. 58 is the oscillation signal input terminal of vCO, 5
9 is a frequency division output terminal, 60 is a band voltage output terminal, 61 is a fixed frequency divider, and 62 is a counter.

63 is a band voltage generator, 64 is a decoder, and 65 is a latch circuit. Input from oscillation signal input terminal 58 7'2
The VCO signal is frequency-divided by a fixed frequency divider 61, and a portion of the frequency-divided signal is supplied to the PLL circuit via a frequency-divided output terminal.

The frequency-divided signal is counted by a counter 62 for a clock period based on the clock signal of the clock generator, and this counting result is input to a decoder 64 to be outputted from a plurality of gates, and this gate output is used to generate a band voltage. The circuit 65 holds the voltage for a period corresponding to the clock period and simultaneously outputs it as a band voltage. The band voltage generation circuit generates a band voltage by directly converting the information from the decoder 64 into a band voltage, or by comparing the decoded information with information previously set in a ROM, etc. according to the receiving frequency band. Possible methods include:

〔Effect of the invention〕

According to the present invention, the band voltage for switching the reception frequency band is obtained using the output signal of the fixed frequency divider, so the connection between the electronic tuner and an external circuit is simplified, and at the same time, the reception frequency band can be switched depending on the frequency. This allows accurate switching. Furthermore, it is also possible to integrate a counter, a decoder, a band voltage generation circuit, a clock generation circuit, etc. together with a fixed frequency divider.

[Brief explanation of drawings]

FIG. 1 is a circuit block diagram showing a first embodiment of the present invention;
FIG. 2 is a circuit diagram showing an example of a tuning circuit, FIG. 3 is a circuit block diagram showing a second embodiment of the present invention, FIG. 4 is a circuit diagram showing an example of the configuration of a bandpass filter, and FIG. FIG. 1 is a circuit block diagram showing a fixed frequency divider according to the present invention. 2... Band pass filter 4... Band pass filter 8 6... VCO 9... Fixed frequency divider 20... Band pass filter 52... First mixer 53... VCO 66...
・Second mixer 37...Fixed oscillator 40...Third mixer 41...Fixed frequency divider 61...Fixed frequency divider 62...Counter 63...Clock generation circuit 64... Decoder 65...Band voltage generation circuit

Claims (1)

[Claims] 1. Using a signal obtained by dividing the oscillation frequency of the voltage controlled oscillator by a fixed frequency divider, the oscillation frequency is determined by a PLL (phase-locked loop) circuit, and the oscillation frequency is determined by a PLL (phase-locked loop) circuit, and In an electronic tuner that receives a high frequency signal such as a television signal by selecting one of the
An electronic tuner characterized in that the electronic tuner has a built-in circuit that outputs a frequency-divided signal of a fixed frequency divider, simultaneously counts the frequency of the signal, and outputs a reception frequency band switching signal according to the counted value. . 2. The electronic tuner according to claim 1, wherein the fixed frequency divider includes a built-in circuit for outputting a reception frequency band switching signal.