JPS63280519A - Receiver - Google Patents

Abstract

PURPOSE:To improve the electromagnetic interference from adjacent channels and the S/N by decreasing the frequency drift in a 2nd intermediate frequency so as to reduce the band width of 2nd intermediate frequency band limit filter. CONSTITUTION:The frequency of a 1st local signal 11 and that of a 2nd local signal 13 are made identical, a 1st intermediate frequency 12 and the 2nd intermediate frequency 14 are set and the selection of the upper and lower band in the mixing of the 1st and 2nd mixers 1, 3 is combined properly to cancel the frequency drift of the 1st local signal 11 and the frequency drift of the 2nd local signal 13. Thus, the band width of the 2nd intermediate frequency band limit filter 4 is reduced to improve the S/N and the electromagnetic wave interference from adjacent channels.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a receiving device, and particularly to a receiving device using a double superheterodyne method that performs reception processing by converting the receiving frequency twice. The present invention relates to a receiving device that improves electromagnetic interference from a channel.

[Conventional technology]

Conventionally, in this type of receiving apparatus, the first local signal and the second local signal are generated by completely different frequency sources, as shown in FIG. FIG. 2 is a block diagram showing the configuration of a conventional double superheterodyne type receiving device, in which a first mixer 1°, a first intermediate frequency band-limiting filter 2. 2nd mixer 3. Second intermediate frequency band limiting filter 4° First local signal generator 5. It is configured to include a second local signal generation section 8 and a first local signal control section 9.

The input signal 10 is mixed by the first mixer 1 with the first local signal 11 supplied from the first local signal generation section 5 which is controlled by the frequency control signal 17 outputted from the first local signal control section 9, and then mixed by the first intermediate signal 10. The signal is converted to a frequency of 12 and provided to the first intermediate frequency band-limiting filter 2.

The first intermediate frequency band number limiting filter 2 limits the frequency band to a predetermined value and then supplies it to the second mixer 3 .

The second mixer 3 mixes the second local signal 13 received from the second local signal generator 8 and the output of the first intermediate frequency band-limiting filter 2 to generate a second intermediate frequency 14.
is generated and supplied to the second intermediate frequency band limiting filter 4, which receives a predetermined frequency band limit and converts it into doubles.
It is output as a reception output using the perheterodyne method.

[Problem that the invention seeks to solve]

In the conventional double superhetero gain type receiving device described above, the first local signal and the second local signal are generated by completely different frequency sources, so if a frequency drift occurs in the first local signal, the first intermediate frequency drifts by the same value as the frequency drift of the first local signal, and in addition, the second local signal causes a frequency drift independently of the first local signal, so the frequency drift value at the second intermediate frequency is equal to the frequency drift of the first local signal. A value obtained by superimposing the frequency drift value of the second local signal on the frequency drift value of the local signal may also occur.

Therefore, the band to be given to the band-limiting filter at the second intermediate frequency is the maximum value of the frequency drift at the second intermediate frequency, when no frequency drift occurs between the first local signal and the second local signal. This has the disadvantage that it is necessary to set the channel to be wider than , which inevitably leads to severe disadvantages in terms of signal-to-noise ratio and electromagnetic interference from neighboring channels.

It is an object of the present invention to eliminate the above-mentioned drawbacks, to significantly reduce the bandwidth of the second intermediate frequency band-limiting filter compared to conventional systems, and to significantly improve the signal-to-noise ratio and electromagnetic interference from trusted channels. An object of the present invention is to provide a receiving device using a double-super-edge login method.

[Means for solving problems]

The device of the present invention is a double superheterodyne type receiving device that performs reception processing by frequency converting a receiving frequency twice.
a mixer, a first intermediate frequency band limiting filter that limits the frequency band at the first intermediate frequency, a second mixer that converts the first intermediate frequency to a second intermediate frequency, and a frequency band limiting filter at the second intermediate frequency. a second intermediate frequency band limiting filter that generates a first local signal; a first local signal generating section that generates a first local signal; a frequency changing section that divides the frequency of the local signal to generate a second local signal; The signal generation section is configured to include a control section that outputs a control signal of the generated frequency, and the frequency change section outputs a control signal of the frequency division number.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of the present invention, in which a first mixer 1. First intermediate frequency band limiting filter2. Second
Mixer 3. Second intermediate frequency band limiting filter4. First local signal generation section 1 frequency change section 6. It is configured to include a control section 7.

The operation is as follows. That is, the first mixer 1 mixes the input signal 10 with the first local signal 11 output from the first local signal generator 5, and generates the first intermediate frequency 12.
Output. The first intermediate frequency band limiting filter 2 is
The first intermediate frequency 12 is filtered in a predetermined frequency band and output to the second mixer 3.

The second mixer 3 mixes the second local signal 13 output from the frequency changing section 6 and the output of the first intermediate frequency band limiting filter 2, and outputs a second intermediate frequency 14. The second intermediate frequency band limiting filter 4 filters the second intermediate frequency 14 in a predetermined frequency band and outputs the filtered signal. The control unit 7 outputs the frequency control signal 15 to the first local signal generation unit 5, and the first local signal generation unit 5, which has received this, uses the frequency control signal 15 to output the first frequency control signal 15, which is its output.
Determine the frequency of local signal 11.

The control unit 7 also sends a frequency division number control signal 16 to the frequency change unit 6.
Output. The frequency division number control signal 16 determines the frequency division number in the process of changing the first local signal 11 performed by the frequency changing unit 6, and the frequency division number control signal 16 is the first local signal that changes according to the frequency control signal 13. 11 to a fixed second local signal 13.

Note that the frequency of the second local signal 13 does not always have to be the same, and a negligibly small frequency difference can be tolerated for reception purposes, so if it can be set within this tolerance range, the frequency division number in the frequency change unit 6 There is no need to configure it complicatedly.

Through such an operation, the frequency drift in the first local signal 11 is transmitted to the second local signal 11.

Further, since the frequency drift value of the second local signal 13 is created by frequency-dividing the first local signal 11, the frequency drift value of the first local signal 11 is changed to the frequency drift value of the first local signal 11 by the frequency change unit 6. It is only the frequency divided by the frequency division number, and there is no need for other drift components to exist.

Therefore, by appropriately combining the first intermediate frequency 12 and the second frequency setting and the upper wave body and lower wave body in the mixing in the first mixer 1 and the second mixer 3, the frequency drift value of the first local signal 11 can be adjusted. It becomes possible to easily cancel out the frequency drift value of the second local signal 13, and therefore it becomes possible to significantly suppress the drift value of the second intermediate frequency.

Below, the relationship between the frequency drift of the second local signal of the first local signal and the frequency drift of the second intermediate frequency will be further explained in detail for the conventional example and this embodiment.

Fig. 3(a) is a power versus frequency characteristic diagram of the first local signal when a frequency drift occurs in a conventional receiving device, and Fig. 3(b) shows the power versus frequency characteristic of the first local signal when a frequency drift occurs. FIG. 3(c) is a power vs. frequency characteristic diagram of the second intermediate frequency when a frequency drift occurs in the first and second local signals. As is clear from Figure 3, 3(a)
The figure shows a comparison between the state in which a frequency drift △f, indicated by a dotted line, has occurred in the first local signal 11 and the input signal, and FIG. A state in which a frequency drift Δf2 in the opposite direction occurs and a state in which the position of the original first intermediate frequency 12 is shifted by the frequency drift value Δf of the first local signal 11 are both shown.

Further, FIG. 3(c) shows a state in which the position of the original second intermediate frequency 14 including the mixing operation is shifted by Δf, +Δf2=Δf3 due to drift. This shows that it is likely that the frequency drifts of the local signal and the second local signal will overlap.

4(a) is a power vs. frequency characteristic diagram of the first local signal when a frequency drift occurs in the embodiment of FIG. 1, and FIG. 4(b) is a power vs. frequency characteristic diagram of the first local signal when a frequency drift occurs
Power versus frequency characteristic diagram of intermediate frequency and second local signal. FIG. 4(c) is a power versus frequency characteristic diagram of the second intermediate frequency when a frequency drift occurs in the first and second local signals.

In this case, the frequency drift value Δf4 of the second local signal
is the drift value of the first local signal divided by the frequency division number. That is, Δf4=Δf1/n (n=frequency division number). Then, the frequency drift values of the second intermediate frequency 14 cancel each other out and become the difference Δf5 between Δf1 and Δf4. As mentioned above, Δf5 can be made almost zero.

〔Effect of the invention〕

As explained above, the present invention provides a first local signal and a second local signal.
By setting the frequencies of the local signals to be the same and selecting such that the frequency drift value of the first local signal and the frequency drift value of the second local signal cancel each other out, the frequency drift value at the second intermediate frequency is reduced. This method has the advantage that the bandwidth of the frequency band-limiting filter can be made smaller than that of the conventional method, and characteristics can be significantly improved in terms of signal-to-noise ratio and electromagnetic interference from neighboring channels.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the double superheterodyne receiver according to the present invention, FIG. 2 is a block diagram of a conventional double superheterodyne receiver, and FIG. 3(a) is a block diagram of a conventional double superheterodyne receiver. Figure 3(b) shows the power vs. frequency characteristic diagram of the first local signal when a frequency drift occurs in a conventional receiving device.
A power versus frequency characteristic diagram of the intermediate frequency and the second local signal, FIG. 3(C) is a power versus frequency characteristic diagram of the second intermediate frequency when a frequency drift occurs in the first and second local signals, and FIG. a) Figure 4(a) shows the power versus frequency characteristic of the first local signal when a frequency drift occurs in the embodiment of Figure 1, and Figure 4(b) shows the first intermediate frequency and frequency characteristics when a frequency drift occurs. FIG. 4(c) is a power versus frequency characteristic diagram of the second intermediate frequency when a frequency drift occurs in the first and second local signals. DESCRIPTION OF SYMBOLS 1... First mixer, 2... First intermediate frequency band limiting filter, 3... Second mixer, 4... Second intermediate frequency band limiting filter, 5... First local signal generation section , 6... Frequency changing section, 7... Control section, 8
. . . second local signal generation section, 9 . . . first local signal control section. 'f33(C) hill d

Claims (1)

[Claims] In a double superheterodyne receiving device that performs reception processing by converting a reception frequency twice, the receiver includes a first mixer that converts an input signal at a first intermediate frequency, and a first mixer that limits a frequency band at the first intermediate frequency. an intermediate frequency band-limiting filter, a second mixer that converts the first intermediate frequency to a second intermediate frequency, a second intermediate frequency band-limiting filter that limits the frequency band at the second intermediate frequency, and a first local signal. The first occurrence
a local signal generator, a frequency changer that divides the frequency of the local signal to generate a second local signal, and outputs a control signal of a generated frequency to the first local signal generator and divides the frequency to the frequency changer. 1. A receiving device comprising: a control section that outputs a frequency control signal.