JPS5928291B2 - dual band radio receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a multi-band radio receiver equipped with an automatic search and tuning function, which automatically switches to another band when no broadcast is detected within the band being automatically searched and selected. This allows the user to continue selecting channels.

The frequency bands of radio broadcasting are FM band and AM
Broadly divided into bands, SW bands, etc.

The SW (short wave) band is usually divided into 3 ME (300 MHz to 30 MHz band) and each is called a band, so each of the divided small bands will also be referred to here. It's called a band.

A plurality of broadcast radio wave frequencies are assigned to each of these bands, and one of these frequencies is selected to receive a desired broadcast.

In a radio receiver equipped with an automatic search/tuning function, if a search station and its band are designated by a switch operation, the tuning operation for that band is dynamically performed.

For example, if you specify an FM band, broadcasts within the same band will be automatically selected and received.

However, due to the small number of FM broadcast stations in Japan, there are many areas where FM broadcasts cannot be received.

When traveling in such areas by car or the like, you will not be able to receive anything even if you specify the FM band and automatically tune in, but if you specify the AM band, you will often be able to receive broadcasts.

Therefore, if you want to receive some kind of broadcast with a radio receiver equipped with an automatic tuning device, you can simply switch to the AM band if it is not received in the FM band, but in the past, this was a hassle and had to be done manually. .

The present invention provides a channel selection device that further enhances the automatic channel selection function by automating the band switching described above.

Hereinafter, the present invention will be described in detail with reference to illustrated embodiments.

FIG. 1 is a block diagram of a conventional multi-band radio receiver having an automatic tuning function.

This receiver uses a voltage variable capacitance element (varacta diode)
This is a so-called electronic tuning method in which tuning is achieved by applying a variable bias voltage to and changing the capacitance, and an analog memory (voltage storage element) or the like is used as the variable bias voltage source.

The receiver of this example has two bands including an FM tuner 1 and an AM tuner 2, and power +B is selectively applied to each tuner by a band changeover switch SB.

RF of tuners 1 and 2 is a high frequency amplification stage (antenna circuit)
, LO is local oscillator, MIX is frequency conversion sound 11k I
F is an intermediate frequency amplification stage, DET is a demodulation (detection) section,
The antenna ANT and the audio frequency amplification stage AF are shared to drive the speaker SP.

Since these operations are known, a detailed explanation will be omitted, but in the electronic tuning type, the output voltage (variable bias voltage) VB of the analog memory 3 is used to control the local oscillator LO and the high frequency stage RF.
The capacitance of the variable capacitance diode changes, and the switch SB
Automatic tuning is performed within the band specified by .

For example, as shown in the figure, if the switch sB is switched to the BFM side, the power is turned on to the FM tuner 1, and when the uplink search selection button SU is pressed, the flip-flop FF1 is reset, the flip-flop FF2 is set, and the signal is passed through the AND gate G2. An H (high) level signal is applied to the switch circuit 4, and the analog memory 3 receives the positive signal ei and outputs a gradually increasing voltage vB, thereby gradually increasing the receivable frequency of the FM tuner 1.

In this way, uplink search and channel selection is performed.

When switch SD is pressed, flip-flop FF1.
FF2 is set and switch circuit 4 is AND gate G
An H level signal is applied through the analog memory 3 to produce a negative output ei, and the analog memory 3 gradually decreases the voltage vB, thereby performing a downward search channel selection.

If the switch SB is switched to the BAM side, such automatic tuning will be performed in the AM band, and the output of the intermediate frequency stage IF (
When the broadcast detection signal (broadcast detection signal) enters the flip-flop FF2 through the gate G1 and resets it, the switch circuit 4 loses its input and ei becomes zero, and the analog memory 3 stops changing the voltage vB.

This stops the channel selection operation and enters the receiving state.

The reception frequency is displayed on the display 9.

A reference signal generation circuit 6 including a crystal oscillator 5 generates a sampling pulse GT, samples the oscillation frequency of the local oscillator LO for a certain period of time, and a counter 7 that is reset by a pulse R8 counts this.

Since this count value corresponds to the reception frequency, it is decoded and the reception frequency is displayed on the display 9 as numbers or bright line lengths.

Conventionally, the automatic search and selection operation described above is performed only within a specified band, and when the upper or lower limit is reached, the search direction is reversed and the currently searched area is searched in the opposite direction again (called triangular wave sweep). Alternatively, it has only been considered to momentarily return to the opposite end at the upper or lower limit and perform the same upward or downward search and selection again (referred to as a sawtooth wave sweep).

In the present invention, the part corresponding to the switch SB in FIG.
With the configuration shown in the figure, if a channel cannot be selected, the band is automatically switched and the next band is searched and viewed.

In FIG. 2, the FM upper limit detection gate G5 detects the upper limit frequency of the FM band using the output of the decoder 8.
The upper limit detection gate G6 detects the upper limit frequency of the AM band, and the lower limit detection gate G7 detects the lower of the lower limit frequencies of both the AM and FM bands.

This is because the count value of the counter 7 indicates the receivable frequency of the receiver, and the upper and lower limit frequencies of the FM and AM bands are known. This is possible by connecting to the appropriate one.

The outputs of these detection gates G5 to G7 (one pulse is generated at the time of detection) are sent to the second counter 2 through OR gate G3.
It is counted as 0.

Since the counter 20 is cleared regardless of whether the switch SD or SU is turned on, the counted value is the upper limit or lower limit (generally referred to as edge) number after the start of channel selection.

However, gate G5. Since G6 is controlled to open and close by the voltage of the power supply terminal BFMtBAM of the AM and FM tuners, the count value of the counter 20 is for the same band.

Note that this receiver uses the aforementioned sawtooth wave or triangular wave sweep for channel selection.

The gate G detects from the count value of the counter 20 whether the automatic search selection has been performed completely within the same band, that is, between the upper and lower limits.For example, in the case of a triangular wave sweep, there are two edges. If it is detected, it means that the upper and lower limits have been completely swept, so the AND gate G is
, generates an H level output and turns on transistor TR3.

If it is desired to perform automatic tuning multiple times within the same band, the AND gate G9 may output an H level output when the count value is "3" or more.

FF3 is a toggle flip-flop driven by a clock pulse to temporarily turn on transistor TR3, and its Q and Q outputs exclusively turn on and off transistors TR1 and TR2.

Therefore, transistors TR1 and TR2 have the function of switch sB in FIG.

Note that the switch 21 arranged in parallel with the transistor TR3 is designed to allow band switching by manual operation, and is normally in an off state.

To explain the channel selection operation of the device shown in FIG. 2 while also referring to FIG. 1, when the switch SU is turned on, the counter 2
0 is once cleared and the flip-flop FF1. F
The gate G2 is turned on by the signal of F2, and the switch circuit 4 is turned on.
A positive voltage e1 is output from.

As a result, the output voltage vB of the analog memory 3 starts to gradually increase, and the tuning frequencies of RF, LO, etc. are increased in an analog manner.

If a broadcast is detected during this automatic channel selection, flip-flop FF2 is reset and gate G2. G3 is closed and memory 3 retains the voltage at that position.

However, if a broadcast is not detected on the way, the upper limit of the band is reached, the voltage is automatically reversed, and the voltage vB starts to drop (in the case of triangular wave sweep).

Then, when the lower limit is reached, a pulse is output from the gate G7, the counter 20 receives this and the count value becomes 2, and the AND gate G9 generates an output and switches the band.

When the switch SD is pressed or when the sweep is a sawtooth wave, the same operation is performed except that the sweep direction is different.

Incidentally, if the transistor TR3 is directly driven by the output of the gate G8, automatic tuning is achieved in which the FM band and AM band are alternately switched each time an edge is detected.

This method is suitable when applied to a shortwave receiver, since it is possible to start a search from a certain band, for example in the upstream direction, and then switch to a high frequency band one after another and sweep the search until a channel is selected.

In this case, an n-advanced switching counter is used in place of the toggle flip-flop FF3, and is shifted by 1 bit each time the transistor TR3 is turned on, so that the output of each stage of this counter automatically switches the n-band.

FIG. 3 shows an embodiment of the present invention applied to a PLL synthesizer type radio receiver.

This receiver has an automatic tuning function for each of three bands: A band, F band, and S band, but the tuner part and the like are omitted.

In the PLL (phase locked loop) synthesizer method, by changing the frequency division ratio N of the variable frequency divider 32, the local oscillator L
Change the frequency of Q.

Sweeping can be performed by continuously changing the N value.
This sweep also ranges from the lower limit (fmin) to the upper limit (fma) of the band.
x), which gradually increases to fmin and then decreases again to fmin, and fm which gradually increases from fmin to fmax and then immediately
A sawtooth pattern that returns to in and gradually increases to fmax again is possible.

In this example, it is the latter. Further, a variable capacitance element is used in the tuning portion of the high frequency stage RF as in FIG. 1.

Fixed frequency divider 30 and phase comparator 3 that create the reference signal in Figure 3
1. Variable frequency divider 32, low pass filter (LPF) 33
and each band's voltage controlled oscillator (VCO) 348,3
One of 4F and 34A constitutes a PLL.

As will be described later, only one of the transistors TR4 to TR6 is in an on state, and the tuner section power supply Bs for each band is
, B p t B A is 10B.

Therefore, when BA=10B, the vCO 34A operates and its output is guided to the variable frequency divider 32 via the OR gate G1o, where the frequency is divided by N, and the frequency is divided by the phase comparator 31 to the frequency divider 30.
The phase is compared with the reference signal from.

An error voltage according to the frequency division ratio N appears in the output of the phase comparator 31, and this is fed back to C034A through the LPF 33, so the VCO 34A changes the oscillation frequency so that the output of the phase comparator 31 becomes zero. .

This oscillator 34A serves as a local oscillator of the tuner, and oscillates at a frequency specified by the frequency division ratio N of the variable frequency divider 32, and searches and selects a channel by changing the N value.

This also applies to the F band and S band.

The frequency division ratio N is sequentially updated by an up/down (U/D) counter 35.

That is, the U/D counter 35 has a preset frequency division ratio N for each band, and counts up or down based on the clock input to the CP (clock) terminal via the gate Gll.

This clock is taken out from the divider 30, and whether up-counting or down-counting is determined based on the output of flip-flop FF5, that is, the instructions from switches sD and sU.

The read-only memory IJ (ROM) 36 stores Nmin (frequency division ratio corresponding to fmin) and Nmax of each band in advance.
(frequency division ratio corresponding to fmax) is stored, and when a band is specified, this is input to the U/D counter 35 and the edge detection digital JLkK unit 37.

The comparator 37 compares the output of the U/D counter with Nmax (Nm1n) given by the ROM 36, and when they match, sends a pulse (detection signal) a to the edge detection signal counter 38.

Further, a signal is sent to the ROM 36 instructing the U/D counter 35 to preset Nm1n in the case of upper limit detection, and to preset Nmax in the case of lower limit detection.

When the count value reaches a predetermined value, the counter 38 sends a band switching signal C to the ROM 36 to instruct band switching.

Since the count value of the counter 38 means that the band has gone around the band r2j, r3J, etc., the count value when the counter 38 generates the signal C is determined according to the desired number of sweeps.

The decoder 39 receives the band information d from the ROM 36 and turns on any one of the power supply transistors TR4 to TR6.

At this time, since the band information d is an n-bit binary code, it is decoded and latched until the band information d is updated.

As mentioned above, the output of gate G11 is output from U/D counter 3.
5 and increases the N value by +1 (-1) for each pulse, but
If the clock from the frequency divider 30 is 50 Hz, the automatic channel selection speed will be 50 channels per second.

The flip-flop FF controls the opening and closing of the gate G1 in conjunction with the start and stop of automatic channel selection, and the switch SD,
It is set by either SU, and is reset by the output (broadcast detection signal) of gate G1 in FIG.

A flip-flop FF5 indicating the counting direction (■n■) of the U/D counter 35 is set by the switch SD and reset by the switch SU.

The operation of FIG. 3 will be explained with reference to the flowchart of FIG. 4. For example, when the automatic tuning switch SU is pressed during reception on the A band, the U/D counter 35 starts counting in the up direction. A sweep is started (N+-N+1).

Then, the sweep is performed until a broadcast detection signal from the IF stage of the tuner section (not shown) is input through the gate G1, that is, until the flip-flop FF4 is reset.
will continue.

If there is a broadcast detection signal (IF = 1), the broadcast at that position is received and stopped, but if there is no broadcast, it is swept to the upper limit of the band, and the band upper limit detection digital comparator 37 outputs the band upper limit detection signal a. Ru.

Therefore, the count value of the counter 38 becomes "1" (C4-C
+1), Nm1n from ROM 36 to U/D counter 35
is output.

Since Nm1n is preset in the variable frequency divider 35, sweeping is continued from that N value (lower limit frequency of the band) until broadcasting is detected again.

If the upper limit of the A band is reached again and no broadcast is detected (C=2), it is assumed that there is no broadcast within the A band in that area, and the output of the counter 38 is R.
Change the code of band information d output from OM36,
The decoder 39 switches to the F band.

After that, the F-band Nmin is stored in the ROM36.
/D counter 35 to start sweeping the F band.

If a broadcast cannot be detected even in the F band (there is no broadcast), the band is similarly swept once or more and then switched to the S band.

If IF=1 in any band, it is assumed that broadcasting has been detected, and scanning within the band and band switching are subsequently stopped.

Note that sweeping within a band is performed as follows.

First, when the band is switched, Nm1n is stored in the ROM36.
is input to the U/D counter 35, and its output is input to the variable frequency divider 32.

When the automatic tuning start switch 5U (SD) is turned on, the flip-flop FF4 is set and its output Q is "
H”.

At the same time, the flip-flop FF5 is also set (reset), so its output Q becomes H91 (L''), setting the U/D counter 35 as an up counter (down counter).

Since the gate G11 is still opened by the flip-flop FF, the output 50Hz of the fixed frequency divider 30 causes the U/D
The counter 35 counts up at a speed of 50CH/S (
count down), and increase the N value of the variable frequency divider 32 at the same speed.

For this reason, VCO34A. The frequency of the local oscillator LO receiving the output of 34s gradually increases.

FIG. 5 shows a different embodiment of the present invention applied to a mechanical automatic channel selection receiver.

This receiver uses a motor M as a drive unit, and detects the upper or lower limit of the band from the gear rotation speed and the cam position.

Here, the description will be made assuming that detection is performed based on the position of the pointer 50.

First, when the automatic tuning switch S is turned on, the S-R flip-flop FF6 is set and Q becomes "H", so the transistor TR7 is turned on and the motor M starts rotating.

Motor M has A and B band tuning circuit 51 A t 51
Drive the core of B to sweep (scan) within the band,
At the same time, the dial and scale pointer 50 are moved.

If a broadcast is detected during the sweep, S-R is output from gate G1.
Since the flip-flop FF6 is reset, the motor M stops and receives at that position.

However, when there is no broadcast, the sweep continues, and when the edge of the band is reached, the switch 52D or 52U is turned on by the pointer 50, and the T flip-flop FF7 is driven through the chattering prevention circuit 53.

The flip-flop FF7 turns on or off the relay driver transistor TR8.

As a result, relay RL is driven and the contacts are set to 1. 2 is switched and the motor M rotates in the reverse direction.

If the motor M rotates in the opposite direction and cannot detect the broadcast even when it reaches the opposite end of the band, it is assumed that the broadcast cannot be detected even after sweeping the band once or more, and the count value of the counter 54 is set to ``2''. The T flip-flop FF8 is driven by the output pulse of the detection circuit 55 which detects the Q.

The tuning circuits 51 A and 51 B are switched by the output, and the motor M starts sweeping in different bands.

As described above, in the present invention, a multi-band radio receiver with an automatic tuning function performs band switching and continues sweeping until a broadcast is detected. If there is, there is an advantage that the broadcast can be received without manual band switching.

This is not only a multi-band radio receiver that can select and receive different bands such as FM, AM, and SW, but also a shortwave radio receiver that can receive by dividing the SW band into many smaller bands for the purpose of increasing resolution. It is also effective when applied to radio receivers.

Furthermore, when selecting a search channel, the number of edge detections within the same band is counted, and when the number of times reaches a predetermined number, the shift is made to another band, which has the advantage that there is no area left unsearched within one band. has.

In addition, when combined with an automatic sensitivity switching device, it becomes possible to perform precise automatic channel selection by checking the presence or absence of weak radio wave broadcasts before switching bands.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a conventional electronically tuned radio receiver having an automatic tuning function, and FIG. 2 is a block diagram of main parts showing an embodiment of the present invention applied to the receiver shown in FIG. Third
The figure is a block diagram showing another embodiment of the present invention applied to a PLL synthesizer type radio receiver, Figure 4 is a flowchart explaining the operation of Figure 3, and Figure 5 is a mechanical automatic channel selection radio reception. FIG. 2 is a block diagram showing different embodiments of the present invention applied to a machine. In the figure, G5. G6 is an upper limit detection gate, G7 is a lower limit detection gate, 20.38, 54 is an edge detection signal counter, F
F3 is a toggle flip-flop for band switching, 37 is an edge detection digital comparator, 39 is a decoder for band switching, and FF8 is a T flip-flop for band switching.

Claims (1)

[Claims] 1. In a multi-band radio receiver having an automatic search tuning function, a circuit that outputs an edge detection signal when the received frequency during automatic search tuning reaches the edge of a band, and an output from the circuit. a circuit that includes a counter that counts the number of times the signal is received within the same band and generates a band switching signal when the count of the counter reaches a predetermined number; and a circuit that receives the band switching signal and selects the next search station. 1. A multi-band radio receiver comprising: a band switching circuit for switching one band to another. 2. A patent characterized in that the band switching circuit consists of a flip-flop whose state is inverted by the output of the band switching signal generation circuit, and a pair of switching elements that are driven at the Q and Q ends of the flip-flop to turn on and off the tuner power supply. A multi-band radio receiver according to claim 1. 3. The band switching circuit consists of an n-advanced switching counter that is shifted by one bit by the output of the band switching signal generation circuit, and a plurality of switching elements that are driven by the output of each stage of the counter to turn on and off each tuner power supply. A multi-band radio receiver according to claim 1.