JPH0241015A - Receiver with synthesizer tuner - Google Patents

Abstract

PURPOSE:To change an inter-station frequency without extending a key such as a manual switch by discriminating it that the inter-station frequency is kept or changed to the different inter-station frequency based on the 1st and 2nd comparator outputs formed by an FM detection output. CONSTITUTION:An FM detection output in an FM detection means 50 is fed to a center meter 51 and also fed to comparators 60, 65. Reference values V1, V2 are set as voltages corresponding to frequencies f1, f2 while clipping a center frequency f0. Thus, when the swept frequency is lower than the center frequency f0 by 5kHz, a negative comparison output C1 is obtained from the comparator 60 and when the swept frequency is higher than the center frequency f0 by 5kHz, a positive comparison output C2 is obtained from the comparator 65, and a pointer of the center meter 51 is deflected negatively or positively. When the comparison outputs C1, C2 are obtained by the adjacent inter-station frequency, it is discriminated that the reception frequency exists inbetween and the inter-station frequency is revised.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention is applicable to a receiver equipped with a synthesizer tuner such as a synthesizer type AM/FM receiver, in particular, to adjust the AM interstation frequency without adding operation keys. Regarding a receiver that allows you to change such things.

[Prior Art] A receiver having a synthesizer tuner, for example, a synthesizer type AM/FM receiver, can automatically select a broadcast station within its reception area by automatically sweeping the reception frequency. In that case, the sweep frequency step is usually selected to be the inter-office frequency.

Otherwise, it may take time to select a channel, or the target broadcast station may be skipped, making it impossible to receive it.

As is well known, in the case of AM receivers, the inter-office frequency is selected to be 10 KHz in the United States and Canada, and 9 KHz in other areas including Japan.

For FM receivers, 200K in the US and Canada
Hz, and in other areas, the inter-office frequencies are selected in steps of 100 KHz.

Further, in the case of an FM receiver, in addition to the inter-office frequency, de-emphasis characteristics differ depending on the inter-office frequency.

If the inter-station frequency is 200 KHz, 75 μs
c (approximately 13.3 KHz), whereas if the inter-station frequency is 100 KHz, the
sec (approximately 20.0 KHz).

[Problem to be solved by the invention] Incidentally, with the development of transportation means in recent years, cross-border traffic is becoming more prominent, and along with such human exchange, broadcasting equipment such as AM/FM receivers etc. Receiving equipment is also increasingly being carried around when traveling back and forth.

Particularly in countries such as Japan and the United States, which have deep economic ties, there is active exchange between both businessmen and tourists.

In such a case, for example, if you travel to the United States with the AM/FM inter-station frequency set to 9KHz on your AM/FM receiver in Japan, if you leave the AM inter-station frequency as it is and automatically sweep it, you will not be able to find the broadcast stations that can originally be received in the United States. Even the messages are skipped, making it impossible to receive them. This is because, as mentioned above, the AM inter-office frequencies are different between Japan and the United States.

On the contrary, AM/F whose AM interstation frequency was set to 10KHz in order to receive broadcast stations in the United States.
Even when the M receiver is used in Japan, the same problem as mentioned above will occur.

In order to eliminate such problems, in the past, a manual switch was built into the set to change the frequency between AM stations.In cases where the frequency between AM stations differs due to different receiving areas, this manual is used. AM within the reception area by operating the switch.
I was trying to match the inter-station frequency.

However, providing this type of switch increases the cost of the device.

On the other hand, the synthesizer type AM/FM receiver has a built-in microcomputer for controlling the synthesizer tuner as described above. In that case,
If the microcomputer and manual switch are installed in a set with a distance between them, that line will act as an antenna line, which may cause unnecessary radiation to leak outside or pick up external noise. There is.

This may cause a problem of deteriorating the S/N ratio of the received signal.

Furthermore, when receiving FM broadcasting, the de-emphasis characteristics differ depending on the difference in frequency between FM stations, so if the de-emphasis characteristics are not appropriately changed, the sound quality will deteriorate.

In other words, an FM with a de-emphasis characteristic of 50 μSee
When receiving a broadcast, if you listen to an FM broadcast in a reception area where the FM inter-office frequency is 200 KH2 with the de-emphasis characteristic as it is, that is, with the de-emphasis characteristic of 75 μsec, only the high frequencies will be emphasized, which will be extremely This results in a harsh sound quality.

In this case as well, if a dedicated changeover switch is provided as in the case of the inter-office frequency, the same problem as described above will occur.

Therefore, the present invention solves these conventional problems, and proposes a receiver having a synthesizer tuner that can change at least the inter-station frequency without adding keys such as manual switches. It is something.

[Means for Solving the Problems] In order to solve the above-mentioned problems, in this invention,
``It has a detection means for intermediate frequency output, and first and second comparators that compare the detected output with first and second reference values, and the first and second reference values have a center of the detected output. The inter-office frequency to be swept is changed based on the comparison outputs obtained from the first and second comparators.

[Work] The function to be set is at least the inter-office frequency.

The AMM receiver is an AM interoffice frequency, and the FMM receiver is an FM interoffice frequency. In the AM/FM receiver, both inter-office frequencies are changed.

In addition to this, in the embodiment, the FM de-emphasis characteristic can also be changed. Such a change processing operation is executed each time the broadcast station is scanned after the power is turned on.

As shown in Fig. 4, the first and second reference values Vl and V2 are sandwiched between the center Vo of the three-figure curve that is the detected wave output, and the first reference value ■1 is set at the lower frequency than the center Vo. The second reference value v2 is set higher than the center frequency. Here, the fO intermediate frequency is shown.

The intermediate frequency to be swept is changed based on comparison outputs C1 and C2 obtained from the first and second comparators 60.70.

For example, as shown in Figure 5, the frequency of the broadcasting station to be received is 950 KHz, and the sweep station is 9KH2.
When the sweep frequency becomes 945 KHz, the FM detection output between them is lower than the first reference value ■1, so the first comparison output C1 (in this example, a negative output) is obtained, Based on this, the pointer on the center meter 51 swings toward the plus side as shown in FIG.

When the sweep frequency is roughly increased by one step to 954 KHz, it will shift in a direction higher than the center frequency fO. In the example, a positive output) is obtained. As a result, the deflection of the pointer of the center meter 51 is reversed to the negative side.

In this way, when the center meter 51 swings during the sweep steps before and after the frequency to be received, and the state of the swing is reversed, there is a broadcast station to be received between these steps. In that case, the sweep frequency, that is, the inter-station frequency will be changed from 9 KHz to 10 KHz.
Automatically change to Hz step.

In this way, it is possible to easily determine whether the inter-office frequency of the broadcasting station to be received is 9 KHz or 10 KHz based on the intermediate frequency output, and based on this, the inter-office frequency can be adjusted accordingly. It is possible to match the inter-office frequency of the ε band.

[Embodiment] Next, an example of a receiver having a synthesizer tuner according to the present invention will be described using a synthesizer type A receiver as described above.
The application to an M/FM receiver will be described in detail with reference to FIG. 1 and subsequent figures.

In this example, in addition to AM and inter-office frequencies, FM de-emphasis characteristics can also be changed at the same time.

FIG. 1 shows a synthesizer type AM/FM according to the present invention.
It is a system diagram showing an example of a receiver, and 10 is an AM receiver, 70 is an FM receiver, and 20 is a synthesizer tuner provided in common to each.

In the AM receiver 10, 1 is a high frequency amplification circuit, and 2 is a mixer. A synthesizer tuner 20 having a PLL configuration is connected to the mixer 2 .

3 is an intermediate frequency transformer, 4 is an intermediate frequency amplifier circuit, 5 is a narrow band ceramic filter, 6 is an AM detector, 7 is a low frequency amplifier, and 8 is a speaker.

The FM receiver 70 is similarly configured.

71 is a high frequency amplification circuit constituting the front end; 72
is a mixer, 73 is an intermediate frequency transformer, 74 is an intermediate frequency amplification circuit, and 75 is an FM detector. FM detection output is F
After its frequency characteristics are limited by the M de-emphasis circuit 90, it is supplied to the low frequency amplifier 7.

Details of the de-emphasis circuit 90 will be described later.

The synthesizer tuner 20 described above has a PLL configuration. Therefore, the fixed reference oscillator 21 and the variable oscillator 22
．． 26.

In this example, although it is a shared configuration, the variable oscillators 22 and 26
Since the frequency bands are significantly different, a dedicated variable oscillator is used. 22 is a variable oscillator for AM,
26 is a variable oscillator for FM.

Then, one of the oscillation outputs is selected according to the band switching.

The outputs of the variable oscillators 22 and 26 are supplied to the mixers 2 and 72 as their local oscillation signals, and are also supplied to the programmable divider 23, and the divider output and the reference oscillation output of the reference oscillator 21 are phase-compared in the phase comparator 24. The phase comparison output is supplied as a voltage control signal to the variable oscillator 22.26 via the low-pass filter 25.

The programmable divider 23 is supplied with a command signal necessary for receiving a predetermined broadcast station from a microcomputer 30 that controls various controls of this AM/FM receiver, and the programmable divider 23
You can control the programmable 1st shift.

When a broadcast station is received, the signal detectors 40 and 80 provided in each of the AM receiver 10 and the FM receiver 70 amplify and detect the high frequency signal changed to the intermediate frequency. 31 indicates a key operation section.

The FM de-emphasis circuit 90 provided in the FM receiver 70 can be configured as an RC circuit as shown in the figure.
and capacitors C1 and C2 connected in parallel.

A control transistor Q is connected in series to one capacitor C2. The control transistor Q is controlled by the IIJIl] signal from the microcomputer 30.

When receiving FM broadcasts in the United States, etc., the time constant of the FM de-emphasis circuit 90 is set to a larger value than in Japan.
, that is, you have to change it to 75usec,
In that case, the control transistor Q is controlled to be in the on state by the control signal. In this case, since the capacitors C1 and C2 are connected in parallel, the time constant becomes large.

Therefore, the time constant R-CI is 50μSee, and the time constant R-CI is 50μSee.
Each value is selected so that (CI+C2) is 75 μsec.

In this invention, as shown in FIG. 1, an FM detection means 50 is further provided on the output stage side of the intermediate frequency amplification circuit 4 provided in the AM receiver 1o, and the intermediate frequency output is FM detected here. . FIG. 4 shows an example of the 8-character characteristic that is the FM detection output.

The detection output is supplied to the center meter 51 as well as to the first and second comparators 60 and 65.

The first comparator 60 has an operational amplifier 61, and its non-inverting input terminal is supplied with a first reference value 1 determined by series-connected resistors R1 and R2, and its inverting terminal is supplied with a detection value. Output is supplied.

The second comparator 65 has a similar configuration and includes an operational amplifier 66, and the second reference value v2 obtained from the series resistors R3 and R4 can be supplied to the inverting terminal, and the detection output can be sent to the non-inverting terminal. Supplied.

Here, the first and second reference values V1. As shown in FIG. 4, V2 is set as a voltage corresponding to frequencies separated by predetermined frequencies above and below the center frequency fo. That is, in this example, the frequency f1 (= f o −3 to 4
kHz), it can be set to the first reference value Vl. Similarly, f2=fo+3~4KHz
The voltage obtained at this time is set as the second reference value (2).

By doing so, if the frequency just swept is, for example, about 5 KHz lower than the center frequency, a negative comparison output C1 is obtained from the first comparator 60. On the other hand, when the sweep frequency is approximately 5 KHz higher than the center frequency, a positive comparison output C2 is obtained.

Therefore, as shown in FIG. 5, for example, if the broadcast frequency to be received is 950 KHz, the sweep step is selected to be an inter-office frequency of 9 KHz, and the sweep frequency is 945 KHz,
z or 954 KHz, the FM detection output is O, so the pointer of the center meter 51 points to the center (~0).

However, when the sweep frequency becomes 945KHz, 8 in Figure 4
A predetermined FM detection output can be obtained from the relationship between the curves.

Since this detection output is smaller than the first reference value ■1, the first
Only the comparison output C1 is obtained, and the pointer of the center meter 51 swings to the + side (FIG. 5).

When the sweep frequency roughly increases by one step to 954 KHz, it will exceed the second reference value (2). As a result, only the second comparison output C2 is obtained, and
The pointer of the center meter 51 will swing to the negative side (
(See Figure 5).

In this way, when the FM detection output is obtained, it is roughly 1
If the FM detection output is inverted when the sweep frequency is increased or decreased by a step, it means that there is a broadcast frequency to be received between these sweep frequencies (in the above example, between 945 KHz and 954 KHz). .

In that case, the inter-office frequency of the sweep frequency can be changed to 10 KHz.

The reception frequency is a frequency that is lower than the sweep frequency when the sweep is stopped, that is, 954 KHz, is an integral multiple of the inter-station frequency, and is closest to the stop sweep frequency, in this example, 950 KHz. automatically changed to .

In this way, the first and second
When the comparison outputs C1 and C2 of Interval frequency change is performed.

In this example, the FM de-emphasis characteristic is also automatically changed at the same time as the inter-office frequency is automatically changed. That is, in this case, the de-emphasis amount is set to 75 μsec.

Such a series of change processing is carried out by the microcomputer 30.
executed by Therefore, the first and second comparison outputs C1 and C2 are supplied to the corresponding ports of the microcomputer 30.

The microcomputer 30 changes the inter-station frequency based on the first and second comparison outputs CI and C2.
Changes in the reception frequency, changes in de-emphasis characteristics, etc. are executed.

FIGS. 2 and 3 are flowcharts showing an example of a control program for achieving this automatic change of inter-office frequencies, etc.

First, an example of the control program 100 shown in FIG. 2 will be explained.

In the present invention, after the microcomputer 30 is powered on, initial values are set in step 120. In this example, the initial value settings are 9KHz for 3 AM receivers and 9KHz for FM receivers.
In the case of a receiver, the frequency is initially set to 10 KHz, and the de-emphasis amount is set to 50 μsec.

When the setting of the initial pA value is completed, the manual state of the keys provided on the operation unit is read (step 131).
. It then checks to see if any of those keys have been pressed, and in the case of a keystroke other than the up key in this example, which is the frequency sweep key, the sequence of actions corresponding to that key is performed. (Steps 132-134).

When the up key is pressed, the muting operation is immediately executed, the sweep frequency is stepped up by one step, and the first and second comparison outputs C1 and C2 and the signal detection output are read at the increased sweep frequency. I can run (
Steps 135-137).

Among these inputs, especially when the level of the signal detection output SD is checked and there is no signal detection output, the states of the first and second comparison outputs C1 and C2 are determined, and the first comparison output C1 is not 1. If so, the process returns to step 136 and the sweep frequency up operation is executed (step 1
39.136).

By sequentially executing such frequency sweep processing,
When the signal detection output SD becomes high level, the process proceeds to step 141, and the first and second comparison outputs C1 and C2
The state of is determined. At this time, if both the first and second comparison outputs C1 and C2 are not O, step 13
9, it is checked whether the first comparison output C1 is at a high level. If it were at a high level, the sweep frequency would be 945 KHz as shown in FIG. Roughly advance one step and obtain the first and second comparison output CI at that time.
, C2 (151, 152).

At this time, the second comparison output C2 is checked, and when it is at a high level, it is exactly the same as the state of 954KHz in Fig. 5, so in this case, there is a broadcasting station at a frequency lower than 954KHz. It is considered that

As a result, in step 154, the reception frequency and the inter-office frequency are changed, and muting processing is performed. That is, in this example, the receiving frequency is first changed. The change is 954, which is the frequency when the sweep is stopped.
A frequency lower than KHz and an inter-office frequency of 10K
The receiving frequency is changed to a frequency that is an integer multiple of Hz and is closest to 954 KHz (therefore, 950 KHz). Muting processing is performed during the reception frequency change period. Next, the inter-office frequency will change from 9KHz to 10K.
Can be switched to Hz.

After such frequency changing processing is executed, in step 155, the de-emphasis amount is changed. That is, in this example, the de-emphasis amount is changed to 75 μsec, and the FM inter-office frequency is changed to 200 KHz, and then the process returns to step 131.

Note that in step 153, when the second comparison output C2 remains at a low level, step 138 is performed again.
The state of the signal detection output SD is checked again.

Note that when the signal detection output SD is also at a high level and the first and second comparison outputs CI and C2 are at a low level, it means that the sweep frequency is exactly the same as the receiver A3 frequency. In that case, the inter-office frequency changing process is not executed, and at that step, the frequency sweep mode is stopped and the muting state is canceled (steps 142, 143).

FIG. 3 shows an example of the initial value setting routine 120 described above.

First, when the power to the microcomputer 30 is turned on, that is, when the backup power source is turned on, the counter is reset and the input port of the power source for the receiver body is read (step 12).
1.122).

Then, when it is determined that the power switch port on the receiver main body side is in the on state, the counter is incremented (steps 123 and 124). In the above example, the first turning on of the power switch immediately after the backup for the microcomputer is completed is detected, and in this case, the process moves to step 126 via step 125.
Interstation frequency change processing is executed. In this example, AM
The initial values can be set so that the inter-office frequency is 9 KHz for the receiver and 100 KHz for the FM receiver.

When these initial value settings are completed, the de-emphasis amount is changed to 50 μsec corresponding to 100 KHz (step 127).

Note that even when the inter-station frequency is set to 10KHz and is changed to 9KH2 using the processing routine described above, the automatic change process is performed while taking into account the first and second comparison outputs C1 and C2. , the explanation thereof will be omitted. However, even in this case, the reception frequency when changing the inter-office frequency is a frequency that is an integral multiple of the inter-office frequency (9 KHz), and is changed to a frequency that is closest to the sweep frequency when the sweep is stopped.

Of course, it is also possible to automatically change the inter-office frequency by sweeping the frequency from a high frequency direction to a low frequency direction.

[Effects of the Invention] As explained above, according to the configuration of the present invention, it is determined whether the inter-station frequency should be maintained as it is based on the first and second comparison outputs formed based on the FM detection output. This is to determine whether to change to a different inter-office frequency.

Therefore, according to the present invention, since the inter-office frequency can be automatically changed, the trouble of manually changing settings can be eliminated.

Of course, since it is not necessary to provide a manual switch for changing the frequency between stations, there is no risk of unnecessary radiation being spread outside or picking up external noise due to this manual switch, and the SN of the received signal is also reduced. can be improved.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of essential parts showing an example of a receiver having a synthesizer tuner according to the present invention, and FIG. 2 is a flowchart illustrating automatic inter-station frequency setting processing and de-emphasis characteristic changing processing. Figure 3 shows an example of a flowchart for initial value setting, Figure 4 shows a characteristic curve showing an example of FM detection output, and Figure 5 provides an explanation of the operation of automatic inter-station frequency change processing. It is a diagram. 4, 74 6, 75 22, 26 40, 80 60, 65 ・Intermediate frequency amplifier circuit・Detector・AM receiver・Synthesizer tuner・Variable oscillatorφ microcomputer・Signal detector・FM detection means・Center meter・First and second comparator/de-emphasis circuit

Claims (1)

[Claims] (1) It has a detection means for intermediate frequency output, and first and second comparators that compare the detection output with first and second reference values, and the first and second reference values are the detection means for the intermediate frequency output. A synthesizer tuner characterized in that the inter-office frequencies to be swept are changed based on the comparison outputs obtained from the first and second comparators, each set at a predetermined level sandwiching the center of the output. receiver with.