JPH0628837Y2 - Multi band receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a multiband receiver, and more particularly to a multiband receiver in which a local oscillator circuit is composed of a phase locked loop.

(B) Conventional Technique As a multi-band receiver in which the local oscillator circuit is composed of a phase locked loop, the one shown in FIG. 3 is conventionally known.

In FIG. 3, (1) is an FM band voltage controlled oscillator (FM VCO) that outputs an FM local oscillation signal, (2)
Is a MW band voltage controlled oscillator (NW VCO) that outputs a MW local oscillation signal, (3) is a SW band voltage controlled oscillator (SW VCO) that outputs a SW local oscillation signal,
(4) is a gate circuit to which the oscillation output from the VCOs (1), (2) and (3) is supplied, and which selects the oscillation output of the VCO corresponding to the band according to the band switching signal, and (5) is the gate circuit ( A programmable frequency divider that divides the oscillation output of the VCO selected in 4) by a frequency division ratio N, and (6) is a frequency division output from the programmable frequency divider (5) and a reference frequency oscillator (7). Phase comparator for comparing with oscillation output, (8)
Is supplied with the phase difference signal from the phase comparator (7), and VC
A low-pass filter that supplies a control voltage to O
The programmable frequency divider, the phase comparator, and the reference frequency oscillator constitute a phase locked loop (PLL).
(9) is a control circuit for setting the frequency division ratio N of the programmable frequency divider (5), which is composed of a microcomputer. Reference numeral (10) is a band changeover switch, and (11) is a RAM in which a frequency division ratio corresponding to a frequency last received in each band is stored.

When the FM band key is operated, the control circuit (9) supplies a band switching signal to the gate circuit (4) and the gate circuit (4) selects the oscillation output from the FM VCO (1). Set the state to enable and FM of RAM (11)
The area corresponding to the band is designated, the division ratio data stored in the area is taken out, and set in the programmable frequency divider (5).

In addition, when the SW band key is operated in the FM receiving state, the control circuit (9) supplies a band switching signal to the gate circuit to cause the gate circuit (4) to switch to the SW VCO (3).
Set the oscillation output from the
The area corresponding to the SW band of (11) is designated, the division ratio data stored in the area is taken out and set in the programmable frequency divider (5).

(C) Problem to be solved by the invention By the way, in this kind of multi-band receiver, since the low-pass filter for supplying the control voltage of the VCO is shared, the PLL is used.
It is very difficult to set the loop gain of to the optimum value for all bands.

Therefore, in general, it was designed to optimize the loop gain in a certain band, but if the loop gain in a specific band is prioritized, it takes a lot of time for the loop to stabilize when receiving another band. It may be necessary or, in the worst case, the oscillation frequency of the VCO may be outside the pull-in range of the PLL, and the tuning control may not be performed. In particular, the latter problem was remarkable when the band other than the SW band was switched to the SW band.

(D) Means for Solving the Problems In view of the above points, the present invention provides a voltage controlled oscillator provided for each band, a programmable frequency divider that divides an output from the voltage controlled oscillator by a frequency division ratio N, A phase comparator that compares the frequency division output of the programmable frequency divider and the oscillation output of the reference frequency oscillator, and a phase that is supplied with the output from this phase comparator and that comprises a low-pass filter that supplies a control voltage to the voltage controlled oscillator. A multi-band receiver in which a local oscillation circuit is configured by a synchronous loop, and at the time of band switching, temporary frequency division ratio data is temporarily set in the programmable frequency divider and then regular frequency division ratio data is set. A control circuit is provided.

Further, the provisional frequency division ratio data is frequency division ratio data relating to an end frequency in the reception band before the band switching operation.

(E) Operation According to the present invention, at the time of band switching, the end frequency in the reception band before the band switching is once set to, for example, the lower limit frequency, and then set to the frequency in the selected band.

(F) Embodiment FIG. 1 is a block diagram of an essential part showing an embodiment of the present invention. The same parts as those in FIG. 3 are designated by the same reference numerals and the description thereof is omitted.

In FIG. 1, reference numeral (12) is a ROM for storing the division ratio corresponding to the end frequency of each reception band, which is addressed by the control circuit (9 ') at the time of band switching.

Next, the operation will be described with reference to FIG.

If it is in the FM reception state now, FM VCO (1)
Is oscillated from the reference frequency oscillator (7) in the phase comparator (6) after being divided by N by the programmable frequency divider (5) and then supplied to the phase comparator (6). Be compared. As a result of the phase comparison, if there is a phase difference between the two signals, the control voltage corresponding to the phase difference is F
It is supplied to the MVCO (1), so that a stable local oscillation signal is obtained.

When the SW band key of the band changeover switch (10) is operated in such a state, the control circuit (9 ') first outputs a muting control signal and outputs the muting control signal to the muting circuit (Fig. (Not shown). Next, the area corresponding to the FM band of the ROM (12) is designated and the frequency division ratio data corresponding to the end frequency (for example, lower limit frequency) of the FM band is read out and set in the programmable frequency divider (5).

After the PLL locks at the local oscillation frequency corresponding to the lower limit frequency, the control circuit (9 ') supplies the band switching signal to the gate circuit (4) to select the oscillation output of the SW VCO (3) and the RAM. The area corresponding to the SW band of (11) is designated, the division ratio data corresponding to the frequency previously received in the SW band is read, and set in the programmable frequency divider (5).

After that, it is determined whether or not a predetermined muting time has elapsed, and when the predetermined time has elapsed, the polarity of the muting control signal is inverted to cancel the muting.

Thus, although the conventional problem is solved, the provisional frequency division ratio data set at the time of band switching includes not only the frequency division ratio data corresponding to the end frequency but also the frequency division ratio of the frequency close to the band to be switched. I wish I had it. Further, in the embodiment, the operation at the time of switching from the FM band to the SW band has been described, but the same may be performed in other cases.

(G) Effect of the invention According to the invention, when the band is switched, the provisional frequency division ratio data is set, and then the regular frequency division ratio data is set in the programmable frequency divider. Since it can be set to the state and the time until the desired frequency is obtained is shortened, the channel selection based on the band switching can be performed quickly.

Further, if the provisional frequency division ratio data is frequency division ratio data corresponding to the end frequency in the reception band before band switching, the time until reception in the changed band can be further shortened.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention, FIG. 2 is a flow chart thereof, and FIG. 3 is a diagram showing a conventional example. (1) (2) (3) ... VCO, (4) ... Gate circuit, (5) ... Programmable frequency divider, (6) ... Phase comparator, (7) ... Reference frequency oscillator, (8) ... Low-pass filter , (9) (9 ′)…
Control circuit, (10) ... band change switch, (11) ... RAM,
(12)… ROM.

Claims (2)

[Scope of utility model registration request] 1. A voltage-controlled oscillator provided for each band, a programmable frequency divider for dividing an output from the voltage-controlled oscillator by a frequency division ratio N, a frequency division output of the programmable frequency divider and a reference frequency oscillator. A multi-band receiver in which a local oscillator circuit is configured by a phase-locked loop including a phase comparator that compares the oscillation output with an output from the phase comparator and a low-pass filter that supplies a control voltage to the voltage-controlled oscillator. A multi-band receiver comprising a control circuit for temporarily setting temporary division ratio data in the programmable frequency divider and then setting normal division ratio data at the time of band switching. . 2. The multiband receiver according to claim 1, wherein the tentative frequency division ratio data is frequency division ratio data regarding an end frequency in a reception band before a band switching operation.