JPS5931071Y2 - multiple band receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a receiver, such as a monitor receiver (described in detail below), which can receive broadcast waves of at least two bands (frequency bands).

In the United States and other countries, a lot of information, mainly news, is transmitted outside the general radio broadcast band whenever information is available.

Such broadcasts are called PSB (Public Service Broadcasting) and their carrier frequencies are 30-5.
0 MHz (LOW VHF band), 150-17
0 MHz (HIGHVHF band), and 450~
The 470 MHz (UHF band) FM signal is widely used for firefighting, security, highway patrol, weather forecasting, etc.

Furthermore, such broadcasts are not transmitted all the time, but are transmitted intermittently only when transmitting information.

Also, broadcast frequencies are usually allocated at intervals of about 30 KHz.

The device that receives such broadcasts is a monitor receiver, and since each broadcast wave has a narrow occupied bandwidth, it is necessary to improve frequency stability, so the receiver's local oscillation circuit is selected by a crystal oscillator and inserted and replaced. A plurality of crystal oscillators provided in a local oscillation circuit are sequentially grounded automatically or manually to switch channels and receive a desired broadcast.

Types of monitor receivers include those for 4 channels capable of receiving four stations, those for 8 to 16 channels, and the like.

Generally, the crystal resonators used in this type of receiver have different specific capacitances depending on whether they are for the VHF band or for the UHF band.

Also, the load capacitance of the crystal resonator must match the specific capacitance of the crystal resonator.

This is because, for example, if a load capacitance with an inappropriate value is used in the local oscillation circuit, the frequency will deviate and oscillate.

Therefore, the load capacitance of the crystal resonator for the VHF band and the UHF pan-N must have a value suitable for each band.

For this reason, this type of receiver has traditionally been used as a VH receiver as shown in Figure 1.
Local oscillation circuits for the F band and the UHF band were provided separately.

In FIG. 1, 1 is a basic oscillator for the VHF band, that is, for both the LOWVHF band and the HIGHVHF band, Ql
11 is a basic oscillator for the UHF band; and Q10 is an oscillation transistor forming the basic oscillator.

Basic oscillator 1, 1 for VHF band and UHF band
', a plurality of crystal oscillators each corresponding to a predetermined broadcast wave of each band are selectively connected by a sweep circuit (not shown); however, in FIG. 1, a crystal oscillator for the VHF band is shown for simplicity will be represented by the symbol X, and the crystal resonator for the UHF band will be represented by the symbol X'.

As is clear from Figure 1, the load capacitance of the water-excited vibrator for VHF band water is composed of the series composite capacitance of capacitors C6 and C1, and the load capacitance of the crystal resonator for UHF band is composed of the series composite capacitance of capacitors C8 and C2. It consists of capacity.

In general, C1>C2, C1 is approximately 60 PF, C, , is approximately 20 PF, and C8 is approximately 100 PF.

Furthermore, figure number 2 is a frequency multiplier for the VHF band connected in cascade to the basic oscillator 1 for the VHF band, and 2' is the frequency multiplier for the VHF band.
This is a frequency multiplier for the UHF band connected in cascade to the basic oscillator 1/ for the HF band.

Conventionally, in this type of receiver, the basic oscillator and the frequency multiplier connected in cascade to the basic oscillator are used for VHF band and UHF band.
Since it was provided separately from the band, there was a drawback that the number of parts increased, leading to an increase in cost.

In view of these points, the present invention solves the above drawbacks by sharing the oscillator (basic oscillator) between the VHF band and the UHF band, and allows stable oscillation to be obtained in each band. An embodiment of the invention will be described with reference to FIG.

In FIG. 2, 1'' is a basic oscillator shared by the VHF band and UHF band, QljF is an oscillation transistor that constitutes the basic oscillator, and the frequency f is determined by the crystal oscillator.

An oscillating voltage of is obtained from the emitter of the transistor q.

This frequency f.

is injected via capacitor C5 into a mixer for the LOWVHF band (not shown).

Note that a plurality of crystal oscillators corresponding to predetermined broadcast waves of each band are selectively connected to the oscillation transistor Q1 by a sweep circuit (not shown), but in FIG. The child is represented by a symbol.

Q2 is a transistor constituting the first-stage frequency multiplier 2"-1, and the collector of this transistor is provided with a tuning circuit 3, which leads from the emitter of the oscillation transistor Q1 to the base of the frequency multiplier transistor Q2. The frequency f.

3 times that is, 3f. The tuning circuit 3 is adjusted so as to be tuned to.

This voltage at a frequency of 3fo is injected into a HIGHVHF band mixer (not shown) via a capacitor C6.

2//, 2 is a second stage frequency multiplier connected in cascade to the first stage frequency multiplier 2"-1, Q3 is a transistor constituting the multiplier, and a tuning circuit 4 is connected to the collector of the transistor. The tuning circuit 4 is tuned to be tuned to three times the frequency 3fo, ie 9fo, which is provided at the base of the transistor Q3.

This voltage at a frequency of 9fo is injected into a UHF band mixer (not shown) via a capacitor C7.

In the circuit shown in Figure 2, the only basic oscillator 1'' is used for both the VHF band and the UHF band, so the load capacitance of the crystal oscillator X'' must be changed between the VHF band and the UHF band. In the embodiment shown in FIG. 2, the configuration of the capacitor connected to the emitter of the transistor Q" of the basic oscillator 1" is devised.

That is, the capacitor C2 is connected to the hot side terminal 5 of the capacitor C3 connected between the emitter of the transistor Qτ and the ground E.
One end of the capacitor C3 is connected to the other end of the capacitor C3, and one end of the first switching diode D1 (ω-sode) is connected to the other end of the capacitor C3.

The other end (anode) of the first switching diode D is configured to be connected to the 10B voltage only when set to the LOW VHF band or the HIGHVHF band by a band switching means such as a band switching switch S. .

(In actual monitor receivers, it is necessary to select a reception band for each channel, so band changeover switches equal to the number of channels are required, but the detailed configuration of the band changeover switch of a monitor receiver is described in Japanese Patent Publication No. 50-13741.
4, etc., so one switch S is representatively shown in FIG. 2 for simplicity.

) A second switching diode D is connected to the connection point 6 between the capacitor C3 and the first switching diode D1.
Connect one end (anode) of 2.

The other end (cathode) of the second switching diode is connected to the hot side terminal 7 of the parallel circuit of the bypass capacitor C4 and the reverse bias voltage setting resistor R, and one end (cathode) of the third switching diode D3 is connected to the other end (cathode) of the third switching diode D3. ) to connect.

The other end (anode) of the third switching diode D3 is connected to a power supply line 8 to which a 10B voltage is supplied only when the UHF band is set by the band changeover switch S.

In this embodiment, the capacitor C3 is about 40 PF.
For the capacitor C4, a capacitor of about 1.0 OOPF is used, and for the resistor R, a capacitor of about 3.3 Ω is used.

The operation of the receiver configured in this manner will be explained next.

First, turn the monitor receiver LOW using the band selector switch.
When set to vHF band or HIGHVHF band broadcast reception status, LOW VHF band or HIGH
A power supply voltage is supplied to a high frequency amplifier circuit and a mixer (both not shown) for the VHF band.

At the same time, since a voltage of 10 B is applied to the anode of the first switching diode D1, the diode D1 and the second switching diode D2 are brought into conduction.

Capacitor C3 is therefore AC grounded via second switching diode D2 and capacitor C4.

Since the value of capacitor C4 connected in series with capacitor C3 is very large, essentially only capacitor C3 is connected in parallel with capacitor C2.

Therefore, the parallel combined capacitance of the secondary capacitors C2 and C3 and the series combined capacitance of the capacitor C8 connected between the base and emitter of the transistor q1 becomes the load capacitance of the crystal resonator for the VHF band.

As is clear from the above description, VH in FIG.
The value of capacitor C1 that constitutes the F-band load capacitance,
The capacitor C is adjusted so that the sum of capacitors C2 and C3 in FIG. 2 is equal, that is, cl-c2+c3.
Since the value of 3 is selected, the load capacitance of the crystal resonator in FIG. 2 is equal to the load capacitance in FIG. 1 when receiving broadcast waves in the VHF band.

Next, switch the monitor receiver to UHF using the band selection switch.
When set to the broadcast reception state for the UHF band, power supply voltage is supplied to the high frequency amplification circuit and mixer (none of which are shown) for the UHF band.

At this time, the voltage of 10B is applied to the third switching diode D3.
A positive voltage is applied to the anode side of the second switching diode D2, and a positive voltage is applied to the cathode of the second switching diode D2 by a resistor R.

On the other hand, since the 10B voltage is not applied to the anode side of the switching diode D1 of the first option, the second switching diode D2 is reverse biased and becomes non-conductive.

Therefore, capacitor C3 no longer constitutes a load capacitance.

Therefore, at this time, since the load capacitance is constituted by the series combined capacitance of capacitors C8 and C2, the load capacitance is constituted by the same capacitor as in the UHF band shown in FIG.

As described above, the present invention allows the load capacitance of the crystal resonator to be changed in accordance with the switching of the band switching means, so that only one oscillator can be used in common for the VHF band and the UHF band, and the parts It is possible to significantly reduce the number of points, simplify the circuit, and reduce costs.

In addition, the load capacitance of the crystal resonator is changed in accordance with the switching of the band switching means, and this load capacitance is made to match the specific capacitance of the crystal resonator in each band, so that the oscillator oscillates at a different frequency. There is no risk, stable oscillation can be obtained, and it is extremely practical.

[Brief explanation of the drawing]

FIG. 1 is a main circuit diagram showing a conventional multi-band receiver, and FIG. 2 is a main circuit diagram showing a multi-band receiver according to the present invention. 1"...Basic oscillator, X"...Crystal oscillator, co. C2, C3...Load capacity, Dl t D2 t
D3...Switching diode, S...
...Band selection switch.

Claims (2)

[Scope of utility model registration request] (1) High-frequency signal receiving means and mixer corresponding to at least two high and low frequency bands, local oscillation means using a plurality of crystal oscillators corresponding to predetermined broadcast waves of each band, and the local oscillation A multi-band receiver comprising a frequency multiplier for multiplying the frequency of the means to a predetermined multiple, and a band switching means, the output of the local oscillation means or the frequency multiplier being supplied to the mixer of each band. The local oscillation means is provided with an oscillator shared by each band, the plurality of crystal oscillators are selectively connected to the oscillator, and the load capacitance of the crystal oscillator is set to be connected to the oscillator for each band. A multi-band receiver characterized in that the load capacitance is changed in response to switching of a switching means so that the load capacitance matches the specific capacitance of the crystal resonator in each band. (2) The load capacitor is composed of a plurality of capacitors, a switching diode is connected to a part of the capacitor, and the switching diode is turned on by a band switching means.
The multi-band receiver according to claim 1, wherein the load capacity is changed according to each band by performing OFF control.