JPS6223146Y2 - - Google Patents

Description

[Detailed explanation of the idea]

The present invention relates to an improvement of a multi-band receiver. Conventionally, for example, in a multi-band radio receiver capable of receiving from a long wave band to a short wave band, the resonant frequency of a local oscillation circuit and the pass band of a high frequency tuning circuit are usually switched for each band in conjunction with each other. This switching was normally accomplished by flipping a band selector switch. For this reason, conventional multi-band radio receivers have disadvantages such as the troublesome band switching and the need to display switching information for each band. In view of this, the present invention is easy to operate because it can automatically switch the band of the high frequency tuning circuit in response to the reception frequency corresponding to the local oscillation frequency by simply changing the oscillation frequency of the local oscillation circuit. The purpose of this paper is to propose a multiband receiver that does not particularly require band switching indications. An embodiment of the present invention will be described in detail below with reference to FIG. This embodiment shows the case where the present invention is applied to a multi-band radio receiver that can receive broadcasts in eight bands from long wave bands to short wave bands.Broadcasts in all bands can be received by simply turning one knob. I am able to receive it. In this radio receiver, the knob manually adjusts the variable capacitor of the local oscillation circuit (main local oscillation circuit) to select a station. The passband for each band of the circuit is automatically switched, and then the local oscillation circuit is switched to control by a PLL frequency synthesizer to maintain the tuned state stably. This PLL frequency synthesizer automatically switches the division ratio of the programmable frequency divider according to the oscillation frequency of the local oscillation circuit during manual adjustment. When controlled by a PLL frequency synthesizer, the minimum change in the oscillation frequency of the local oscillator circuit is determined by the oscillation frequency of the reference oscillator of the PLL frequency synthesizer, so an auxiliary local oscillator circuit that allows you to manually vary the oscillation frequency By mixing the oscillation signal from the auxiliary local oscillation circuit with the oscillation signal supplied from the main local oscillation circuit to the programmable frequency divider, the oscillation frequency of the local oscillation circuit can be substantially changed by the above-mentioned minimum change. It is designed so that it can be changed up to the width below. In FIG. 1, reference numeral 1 denotes a receiving antenna, and its received signal (high frequency signal) is supplied to a high frequency amplifier circuit 3 through a multi-stage switching high frequency tuning circuit 2 and amplified. This amplified high frequency signal is supplied to a frequency conversion circuit (main frequency conversion circuit) 5, converted into an intermediate frequency signal, and outputted to an output terminal 9.
The frequency conversion circuit 5 includes a mixing circuit (main mixing circuit) 6, a local oscillation circuit (main local oscillation circuit) 7, and a bandpass filter 8. The intermediate frequency signal outputted to the output terminal 9 is supplied to a demodulation circuit such as an amplitude detection circuit or a frequency discrimination circuit (not shown) and is demodulated. This local oscillation circuit 7 includes a manually variable capacitor 27 and a variable capacitance diode 31 as variable capacitance elements constituting a resonant circuit, and by varying the capacitance of any one of these variable capacitance elements, the oscillation frequency can be adjusted manually and It is designed to be automatically variable. The multi-stage switching high frequency tuning circuit 2 includes band pass filters 19A to 1 corresponding to the above-mentioned eight bands, respectively.
9H, and on/off switches 20A to 20H and 21A to 2 provided on the input side and output side, respectively.
1H, and band switching is performed by turning on only the input and output switches of one selected bandpass filter. 10 is a PLL frequency synthesizer, the configuration of which will be explained below. The above-mentioned local oscillation circuit (main local oscillation circuit) 7 is connected to this PLL frequency synthesizer 10.
functions as a voltage-controlled variable oscillator. The local oscillation signal from the local oscillation circuit 7 is supplied to a frequency conversion circuit (auxiliary frequency conversion circuit) 26 for frequency conversion, and then supplied to a programmable frequency divider 13 where it is divided by a frequency division ratio of 1/N. be done. This frequency conversion circuit 26 is a mixing circuit (auxiliary mixing circuit)
(including a bandpass filter) 11 and a local oscillation circuit (auxiliary local oscillation circuit) 12. This local oscillation circuit 12 includes a manually variable capacitor 28 forming a resonant circuit, and by varying this, the oscillation frequency can be varied. 14 is a reference oscillator (crystal oscillator), and its reference oscillation signal and the frequency-divided output from the programmable frequency divider 13 are supplied to a phase comparator 15 for phase comparison. The comparison output from this phase comparator 15 is supplied to a low-pass filter 16, and its output is passed through a changeover switch 17 to a local oscillation circuit 7.
is supplied to the variable capacitance diode 31 as an oscillation frequency control signal. 18 is a reference power supply, and when the oscillation frequency of the local oscillation circuit 7 is manually adjusted by the variable capacitor 27, the DC voltage is supplied to the variable capacitance diode 31 through the changeover switch 17, and its capacitance is fixed at a constant value. It is made to be done. This changeover switch 17 is connected to the variable capacitor 2.
Switching is performed by operating a common knob for selecting and adjusting 7 and 28. Reference numeral 29 denotes a control circuit for controlling the multi-stage switching high frequency tuning circuit 2, and is composed of a counter 22 and a decoder 23 to which the output thereof is supplied. Then, the auxiliary local oscillation signal from the auxiliary local oscillation circuit 12 and the mixed signal from the auxiliary mixing circuit 11 are supplied to the counter 22 . As a result, the counter 22 obtains the local oscillation frequency of the local oscillation circuit 7 (or the selected frequency obtained from this local oscillation frequency), and based on this, the decoder 23 determines the band corresponding to the selected frequency and controls it. A signal is generated, which turns on only the on/off switches on the input side and output side of the bandpass filter for that band in the multistage switching type high frequency tuning circuit 2, thereby performing band switching. Further, the frequency division ratio 1/N of the programmable frequency divider 13 is set by the output of the counter 22. 25 is a display that displays the highest frequency in the band and the selected frequency at the time of band switching.The output of the counter 22 is supplied to the decoder 24, and the highest frequency in the band generated from the decoder 24 at the time of band switching is displayed. and display signals of the selected channel frequencies are supplied to the display 25, and these frequencies are displayed. Next, the operation of the multiband receiver shown in Fig. 1 is as follows.
The explanation will be made with reference to the frequency relationship diagram shown in FIG.
Incidentally, the height relationship of each frequency in FIG. 2 is just an example, and the height relationship may be reversed. First of all,
The band names and band frequencies of the eight bands and the corresponding oscillation frequencies of the main local oscillation circuit 7 are shown below.

[Table] Here, Fo is Fo = Fr + Fi. In FIG. 1, Fo is the oscillation frequency of the local oscillation circuit 7, Fr is the reception frequency of the reception signal supplied to the mixing circuit 6, and Fi is the intermediate frequency of the intermediate frequency signal output from the bandpass filter 8. handle. The variable capacitors 27 and 28 are configured to be variable with the same knob; for example, when the knob is pulled, the capacitance of the variable capacitor 27 is varied by rotating it, and when the knob is pushed in, it is rotated. As a result, the capacitance of the variable capacitor 28 is made variable. With the power switch turned on, pull the knob mentioned above. As a result, the changeover switch 17
is switched to the reference power source 18 side. At this time, the capacitance of the variable capacitance diode 31 of the local oscillation circuit 7 is fixed to a constant value depending on the DC voltage of the reference power supply 18. Local oscillation frequency of local oscillation circuit 7
Fo is determined by the capacitances of the variable capacitor 27 and the variable capacitance diode 31. The oscillation signal of the local oscillation circuit 7 is supplied to the mixing circuit 11 of the frequency conversion circuit 26. When the oscillation frequency of the local oscillation circuit 12 is Fd, it is assumed that the frequency of the mixed output of the mixing circuit 11 becomes Fo-Fd. This mixed output is fed to a counter 22 and counted for, for example, one second. Further, the oscillation signal from the local oscillation circuit 12 is also supplied to this counter 22, and is similarly counted for one second. Now, in the frequency conversion circuit 5, if the tuning frequency (reception frequency) is Fr and the intermediate frequency is Fi, then
As described above, there is a relationship of Fi=Fo−Fr between these. In this way, since information on the frequencies Fo-Fd and Fd is given to the counter 22, information on the frequency Fo, which is the sum of both frequencies, can be easily obtained from this information. Also, it can be seen that this frequency Fo has a one-to-one correspondence with the frequency Fr, and the frequency Fo (or
It is also possible to calculate the frequency Fr from Fr=Fo−Fi in the counter 22 (in this case, Fi is the load value), which is supplied to the decoder 23 to select which of the eight bands mentioned above. (or to which band the selected frequency Fr belongs) is determined. and,
According to the determined output of the decoder 22, the bandpass filter of the multi-stage switching high frequency tuning circuit 2 is selected, and only the on/off switches on the input side and output side thereof are turned on. Also, the frequency information Fo from this counter 22
(or Fr) is supplied to the decoder 24, it is determined to which band the selected frequency Fo belongs (or to which band the selected frequency Fr belongs). Further, the highest frequency of that band is determined, and the highest frequency is displayed on the display 25. Therefore, in the multi-stage high frequency tuning circuit 2, by adjusting the variable capacitor 27 of the local oscillation circuit 7, a bandpass filter that passes the corresponding selected frequency is selected according to the local oscillation frequency. Therefore, the variable capacitor 2 of the local oscillation circuit 7
Let us consider a case where the selected station frequency Fr is, for example, 594 kHz within the MW ₁ band. Thus, from Table 1, the intermediate frequency Fi is
Since it is 55.845MHz, the local oscillation frequency Fo of the local oscillation circuit 7 is 594kHz + 55.845MHz = 56.439MHz
becomes. In addition, the local oscillation frequency of the local oscillation circuit 12
If Fd (as an example, this can be changed with an accuracy of about 10kHz around 2MHz, and its variable range is about 100kHz) is 2.1MHz, the frequency Fo−Fd of the output of the mixing circuit 11 is:
56.439MHz−2.1MHz=54.399Hz. Now, as is clear from the above, at this time, in the multi-stage switching high frequency tuning circuit 2, the bandpass filter of the MW ₁ band is in the operating state under the control of the control circuit 29. Therefore, at this time,
The display 25 displays 800 kHz, which is the highest frequency within the MW ₁ band. As described above, the N value of the frequency division ratio 1/N of the programmable frequency divider 13 is set according to the value of the frequency Fo−Fd counted by the counter 22. PLL
When the frequency synthesizer 10 is in the lock state, the reference frequency of the reference oscillator 14 (its value
100 kHz), the relationship between this, the frequency Fo-Fd, and the N value is (Fo-Fd)/N=. Therefore, Fo−Fd=54.399MHz,=100kHz
Substituting into this equation, we get N=543. This corresponds to the value obtained by expressing Fo−Fd in MHz, dividing that number by 0.1, and rounding down the quotient below the decimal point. Next, push in the knob mentioned above. By this,
The changeover switch 17 is switched to the low-pass filter 16 side. This closes the loop of the PLL frequency synthesizer 10 and puts it into operation. At this time, the N value of the frequency division ratio 1/N of the programmable frequency divider 13 is set to 543 as described above. Now, since the N value of the frequency division ratio 1/N of the programmable frequency divider 13 is an integer, it takes a discrete value, and since the N value is determined according to the frequency Fo-Fd rather than the frequency Fo, and Since the DC voltage supplied to the variable capacitance diode 31 becomes the output voltage of the low-pass filter 16 instead of the DC power supply 18, the local oscillation frequency of the local oscillation circuit 7
Fo is slightly off from the 56.439MHz mentioned above, which may cause some out-of-tuning. Therefore, by pushing in the above-mentioned knob and turning it, the local oscillator circuit 1 is set.
If the variable capacitor 28 of No. 2 is adjusted to slightly deviate the local oscillation frequency Fd from the above-mentioned value of 2.1MHz so that the frequency Fo-Fd becomes 54.3MHz, the local oscillation frequency Fo of the local oscillation circuit 7 becomes the above-mentioned value. of
Tuning is performed again after returning to 56.439MHz, and a broadcast with a receiving frequency of Fr=594kHz is received.
Furthermore, Fd [=Fo−(Fo−Fd)]=56.439MHz−54.3M
Hz=2.139MHz. At this time, the frequency Fo−Fd supplied from the mixing circuit 11 to the counter 22=
54.3MHz and local oscillation circuit 12 to counter 22
According to the frequency information of Fd=2.139MHz supplied to the display 25, the corresponding receiving frequency Fr
=594kHz is displayed. To select another frequency, pull the knob again to switch the switch 17 to the reference power source 18 side.
The series of channel selection operations described above will be performed. According to the present invention described above, by simply changing the oscillation frequency of the local oscillation circuit, the bandpass characteristics of the high frequency tuning circuit can be automatically switched for each band according to the selected frequency, and the operation is easy. It is possible to obtain a multi-band receiver that does not particularly require indication of band switching.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a frequency relationship diagram for explaining the same. 2 is a multi-stage switching high frequency tuning circuit, 5 is a main frequency conversion circuit, 6 is a main mixing circuit, 7 is a main local oscillation circuit, 11 is an auxiliary mixing circuit, 12 is an auxiliary local oscillation circuit, 13 is a programmable frequency divider, 14 is a reference oscillator, 15 is a phase comparison circuit, 16 is a low-pass filter, 17 is a changeover switch, 18 is a reference power supply,
22 is a counter, 23 is a decoder, 24 is a decoder, 25 is a display, 26 is an auxiliary frequency conversion circuit,
27 is a variable capacitor, 28 is a variable capacitor,
31 is a variable capacitance diode.

Claims (1)

[Scope of utility model registration request] It has a multistage switching type high frequency tuning circuit, and a frequency conversion circuit consisting of a local oscillation circuit and a mixing circuit, and converts the received high frequency signal from the multistage switching type high frequency tuning circuit into the output of the local oscillation circuit in the mixing circuit. In a multiband receiver that converts the frequency into an intermediate frequency signal by mixing,
A multiband receiver comprising a control circuit for switching and controlling a passband of the multistage switching high frequency tuning circuit in accordance with the oscillation frequency of the local oscillation circuit.