JPH09261286A - Modulator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a desired frequency shift by reducing a tilt of a phase of an oscillation loop. SOLUTION: In the modulator consisting of an oscillation loop with at least an oscillation amplifier circuit 1, a 2-port SAW resonator 3, an oscillation circuit 2, a modulation circuit 2 and a phase shift circuit 4, a coil L or a capacitor C is connected in parallel with a FET switch 2a and connected in series with the oscillation loop. A series circuit consisting of a resistor R2 and a parallel circuit consisting of a capacitor C2 and a coil L2 are connected between the oscillation loop and ground in the phase shift circuit 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to frequency displacement modulation (hereinafter referred to as FSK) used in low power radio equipment and the like.
Type modulator.

[0002]

2. Description of the Related Art Regarding this type of FSK modulator, the present applicant has proposed an invention as shown in FIG. 7 in Japanese Patent Application No. 7-27791. The present invention relates to an oscillation amplifier circuit 1
An FSK type modulator is configured by the 1 and 2 port type SAW resonator 12, the modulation circuit 13 and the phase circuit 14.
Specifically, the Q or phase shift amount of the oscillation loop is adjusted by a parallel circuit of a coil L7 and a capacitor C7 connected from the oscillation loop to the ground. And
The FSK modulation is performed by connecting or short-circuiting a capacitor or a coil connected in parallel with the FET switch.

[0003]

However, according to the previously proposed invention, the phase shift amount largely changes due to a subtle change in the constants of the coil L7 and the capacitor C7 of the parallel circuit, and the frequency shift amount is roughly adjusted. Is very convenient, but it has the drawback that it is difficult to make fine adjustments.

Therefore, the present invention further improves the previously proposed invention to provide a modulator in which the phase inclination of the oscillation loop is reduced to facilitate fine adjustment and to obtain a desired frequency displacement amount. The purpose is to do.

[0005]

In order to achieve the above object, the present invention provides a modulator comprising an oscillation loop composed of at least an oscillation amplifier circuit, a 2-port SAW resonator, a modulation circuit and a phase circuit. , The modulation circuit is F
At least one of a coil and a capacitor is connected in parallel to the ET switch and connected in series to the oscillation loop or between the oscillation loop and the ground, and the phase circuit includes:
A series circuit of a parallel circuit of a capacitor and a coil and a resistor is connected between the oscillation loop and the ground.

Further, according to the present invention, in a modulator comprising an oscillation loop including at least an oscillation amplifier circuit, a 2-port SAW resonator, a modulation circuit and a phase circuit, the modulation circuit includes a FET switch, a coil and a capacitor. At least one of which is connected in parallel and is connected in series to the oscillation loop or between the oscillation loop and the ground, and the phase circuit has a resistor connected to at least one of a capacitor and a coil forming a parallel circuit. , And is connected between the oscillation loop and the ground.

Further, according to the present invention, in a modulator comprising an oscillation loop including at least an oscillation amplifier circuit, a 2-port SAW resonator, a modulation circuit and a phase circuit, the modulation circuit includes a FET switch, a coil and a capacitor. At least one of which is connected in parallel and is connected in series to the oscillation loop or between the oscillation loop and the ground, and the phase circuit includes a parallel circuit formed of a capacitor and a coil between the oscillation loop and the ground. It is characterized in that at least one of a resistor, a coil and a capacitor is connected in series and is connected in series to the oscillation loop.

Further, the present invention is characterized in that a resistor is connected in series to either one of a coil and a capacitor of a parallel circuit which constitutes the phase circuit.

Further, according to the present invention, in a modulator having an oscillation loop formed by at least an oscillation amplifier circuit, a 2-port SAW resonator, a modulation circuit and a phase circuit, the modulation circuit includes a FET switch, a coil and a capacitor. At least one of which is connected in parallel and is connected in series to the oscillation loop or between the oscillation loop and the ground, and the phase circuit includes a first parallel circuit including a first coil and a capacitor, A second parallel circuit including a second coil and a resistor connected to the ground, one end of the second parallel circuit connected to the ground, and the first coil and the second coil electromagnetically coupled to each other. .

Further, the present invention is characterized in that the FET switch of the modulation circuit is connected in parallel to the phase circuit.

As described above, according to the present invention, since the resistance is connected to the parallel circuit of the coil L and the capacitor C connected from the oscillation loop to the ground, the Q of the oscillation loop is connected.
Is moderately damped to the extent that it does not become a loss, the slope of the phase curve is reduced, a desired frequency displacement amount can be obtained, and the output levels of the two frequencies can be equalized.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment circuit of a modulator of the present invention will be described below with reference to FIG. In the figure, 1 is an oscillation amplifier circuit, 2 is a modulation circuit, 3 is a 2-port SAW resonator, 4 is a phase circuit, and these constitute an oscillation loop.

The oscillation amplifier circuit 1 has a field effect transistor Q as its main element, and the power supply voltage Vcc is connected to the drain of the field effect transistor Q through a coil L1. Further, the drain is connected through a capacitor C1. Connected to the output terminal.

The modulation circuit 2 is composed of an FET (field effect transistor) switch 2a. This FET switch 2a
A capacitor C is connected between the drain and the source of the. Further, as shown by a broken line, the coil L can be connected. The drain and gate of the FET switch 2a are connected to the drain of the field effect transistor Q and the modulation signal terminal 2t, respectively.

The 2-port SAW resonator 3 functions as an oscillator, and its input terminal is connected to the source of the FET switch 2a.

The phase circuit 4 includes terminals p1 and p in the oscillation loop.
Two. The internal circuit is as follows. That is, one end of the parallel circuit of the coil L2 and the capacitor C2 is connected to the ground, the other end is connected in series with the resistor R2, and the other end of the resistor R2 is connected to the terminals p1 and p.
2 are connected. The terminal p1 is a 2-port S
It is connected to the output terminal of the AW resonator 3, and the terminal p2 is connected to the gate of the field effect transistor Q.

The circuit of this embodiment has the above-mentioned circuit configuration, and the operation will be described below. Modulation signal terminal 2t
When the FET switch 2a is turned on by the analog or digital modulation signal applied to the capacitor C or the coil L, the circuit of this embodiment oscillates at the first oscillation frequency peculiar to the oscillation loop. On the other hand, when the FET switch 2a is turned off by the modulation signal, the oscillation frequency of the oscillation loop changes due to the combined reactance of the intrinsic reactance of the FET switch 2a and the capacitor C or the coil L, and the oscillation occurs at the second oscillation frequency. Will be done. Therefore, by using the first oscillation frequency and the second oscillation frequency that change according to the modulation signal, FSK modulation can be performed and an FSK modulator can be realized. In the circuit of this embodiment, since the resistor R2 is connected in series to the parallel circuit of the coil L2 and the capacitor C2, Q is appropriately damped and the phase is increased as compared with the case of only the parallel circuit of the coil L2 and the capacitor C2. Becomes smaller, and the output levels of the two frequencies become uniform and stable. Further, the amount of frequency displacement can be finely adjusted by the degree of this damping.

From the viewpoint of the SAW resonator 3, the SAW resonator 3 has the characteristics that the equivalent series inductance is very large and the equivalent parallel capacitance is very small. Therefore, even if some inductance of the coil L is externally connected to the SAW resonator 3 connected in series to the oscillation loop, the oscillation frequency of the SAW resonator 3 does not change so much. On the other hand, S
For the AW resonator 3, a coil L2 and a capacitor C2
If the parallel circuits of are connected in parallel, the oscillation frequency will fluctuate greatly. Therefore, the coil L or the capacitor C connected in series to the oscillation loop is suitable for finely adjusting the oscillation frequency, while the parallel circuit of the coil L2 and the capacitor C2 connected in parallel to the oscillation loop makes the coarse adjustment of the oscillation frequency. Suitable to do.

Next, a second embodiment circuit of the present invention will be described with reference to FIG. The circuit of this embodiment is different from the circuit of the first embodiment shown in FIG. 1 only in the modulation circuit 2. That is, in the first embodiment circuit of FIG. 1, the FE to which the capacitor C or the coil L of the FET switch 2a is connected.
The drain and source of the T switch 2a are connected in series to the oscillation loop, but in the circuit of this embodiment, they are connected to the ground from the oscillation loop. Therefore, in the circuit of this embodiment, when the FET switch 2a is turned on by the modulation signal, the capacitor C or the coil L is short-circuited and the oscillation occurs at the first oscillation frequency specific to the oscillation loop. On the other hand, when the FET switch 2a is turned off by the modulation signal,
Due to the combined reactance of the peculiar built-in reactance of the FET switch 2a and the capacitor C or the coil L, and the reactance of the oscillation loop, the oscillation frequency of the oscillation loop changes to oscillate at the second oscillation frequency. The operation and effect of the circuit of this embodiment is similar to that of the circuit of the first embodiment.

Next, a modification of the phase circuit 4 is shown in FIG.
This will be described with reference to FIG. FIG. 3A shows the phase circuit 4 shown in FIGS. As described above, the resistor R2 is connected in series to the parallel circuit of the coil L2 and the capacitor C2. Note that p1 and p2 are part of the oscillation loop.

The phase circuit 4b shown in FIG. 2B is obtained by removing the resistor R2 shown in FIG. 3A and short-circuiting the resistor R2 and connecting the resistor R2 in series with the capacitor C2 of the parallel circuit.

In the phase circuit 4c shown in FIG. 6C, the resistor R2 shown in FIG. B is removed and short-circuited, and the resistor R2 is connected in series to the coil L2.

The phase circuit 4d shown in FIG. 4D is obtained by connecting a resistor R2 in series with the capacitor C2 shown in FIG.

The phase circuit 4e of FIG. 6E removes and short-circuits the resistor R2 shown in FIG. 9A, and the resistor R2 is seen from the connection end of the parallel circuit and the output side of the field effect transistor Q in the oscillation loop ( p1).

The phase circuit 4f of FIG. 6F removes and short-circuits the resistor R2 shown in FIG. 6E, and the resistor R2 is viewed from the connection end of the parallel circuit, and the input side of the field effect transistor Q in the oscillation loop ( p2).

The phase circuit 4g of FIG. 4G removes the resistor R2 shown in FIG. 3A and short-circuits it, and the coil L3 is seen from the connection end of the parallel circuit.
It is connected to the output side (p1) of.

The phase circuit 4h in FIG. 4H has a capacitor C3 connected in place of the coil L3 shown in FIG. 4G.

In the phase circuit 4j shown in FIG. 4J, the coil L3 is connected in series to the capacitor C3 shown in FIG.

The phase circuit 4k of FIG. 4K has a resistor R3 and a coil L3 on the output side (p1) of the field effect transistor Q in the oscillation loop when viewed from the connection end of the parallel circuit shown in FIG. 3B.
Are connected.

4G, H, J and K shown in FIG.
Since the coil L3 or the capacitor C3 is connected in series to the oscillation loop, the circuit of (2) is suitable for fine adjustment of the oscillation frequency by adjusting the phase amount.

In the phase circuit 4m of FIG. 4M, the resistor R2 shown in FIG. 3A is removed and short-circuited, one end of the coil L3 and the resistor R3 forming another parallel circuit is connected to the ground, and the coil L2 and the coil L3 are connected. And are electromagnetically coupled. The parallel circuit of the coil L2 and the capacitor C2 constitutes, so to speak, the primary circuit of the transformer, and the coil L3 and the resistor R3.
Parallel circuit constitutes a secondary circuit, and these are electromagnetically coupled by mutual inductance, and a secondary current flowing in the secondary circuit flows through the resistor R3, thereby acting as a damping and reducing the phase inclination of the oscillation loop. Will decrease Q. Since this secondary circuit is not directly connected to the oscillation loop, the oscillation loop side can be packaged and the phase can be adjusted from outside the oscillation loop.

Next, a third embodiment circuit of the present invention will be described with reference to FIG. The circuit of this embodiment is a phase circuit 4g.
And the modulation circuit 2 connected in series are provided adjacent to each other, and other parts are almost the same as those of the first embodiment circuit shown in FIG.

The fourth embodiment circuit shown in FIG. 6 is also provided with a phase circuit 4g and a modulation circuit 2 connected in parallel adjacent to each other, and other points are almost the same as those of the second embodiment circuit shown in FIG. Therefore, the same numbers are assigned and the description thereof is omitted.

In the embodiment circuits shown in FIGS. 5 and 6, the phase circuit 4g and the coil and the capacitor in the modulation circuit 2 are also used and interacted with each other, and the rough adjustment and the fine adjustment at the time of manufacturing are collectively performed. be able to.

[0035]

According to the present invention, since the resistance is connected to the parallel circuit of the coil and the capacitor connected from the oscillation loop to the ground, the Q of the oscillation loop is appropriately damped and the slope of the phase curve is increased. Becomes smaller and a desired frequency displacement amount can be obtained. Then, the output levels of the displaced two frequencies are also equalized and stabilized.

Further, according to the present invention, since at least one of the coil, the capacitor and the resistor is connected to the oscillation loop, the amount of phase adjustment can be adjusted by selecting a constant.

Further, according to the present invention, by providing a secondary circuit in the phase circuit, without directly coupling with the oscillation loop,
Its phase or Q can be adjusted.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a first embodiment of a modulator according to the present invention.

FIG. 2 is a circuit diagram of a second embodiment of the modulator according to the present invention.

FIG. 3 is a diagram showing a modification of the phase circuit of the present embodiment.

FIG. 4 is a diagram showing a modification of the phase circuit of the present embodiment.

FIG. 5 is a circuit diagram of a modulator according to a third embodiment of the present invention.

FIG. 6 is a circuit diagram of a fourth embodiment of the modulator of the present invention.

FIG. 7 is a circuit diagram of a conventional modulator.

[Description of Reference Signs] 1 oscillation amplifier circuit 2 modulation circuit 3 2-port type SAW resonator 4 phase circuit L, L1, L2, L3 coil C, C1, C2, C3 capacitor R2, R3 resistance

Claims (6)

[Claims] 1. A modulator comprising an oscillation loop composed of at least an oscillation amplifier circuit, a 2-port SAW resonator, a modulation circuit and a phase circuit, wherein the modulation circuit has at least one of a FET switch coil and a capacitor. Connected in parallel, connected in series to the oscillation loop or between the oscillation loop and ground, the phase circuit, a series circuit of a parallel circuit of a capacitor and a coil and a resistor, between the oscillation loop and ground A modulator characterized by being connected between them. 2. A modulator comprising an oscillation loop composed of at least an oscillation amplification circuit, a 2-port SAW resonator, a modulation circuit and a phase circuit, wherein the modulation circuit has at least one of a coil and a capacitor in an FET switch. Connected in parallel and connected in series to the oscillation loop or between the oscillation loop and ground, the phase circuit has a resistor connected to at least one of a capacitor and a coil forming a parallel circuit, and the oscillation loop A modulator characterized in that it is connected between the ground and the ground. 3. A modulator comprising an oscillation loop composed of at least an oscillation amplifier circuit, a 2-port SAW resonator, a modulation circuit and a phase circuit, wherein the modulation circuit has at least one of a FET switch, a coil and a capacitor. Connected in parallel and connected in series to the oscillation loop or between the oscillation loop and ground, and the phase circuit includes a parallel circuit formed of a capacitor and a coil connected between the oscillation loop and ground. A modulator comprising at least one of a resistor, a coil and a capacitor connected in series to the oscillation loop. 4. The modulator according to claim 3, wherein a resistor is connected in series to either one of a coil and a capacitor of a parallel circuit forming the phase circuit. 5. A modulator comprising an oscillation loop composed of at least an oscillation amplifier circuit, a 2-port SAW resonator, a modulation circuit and a phase circuit, wherein the modulation circuit includes at least one of a FET switch, a coil and a capacitor. Connected in parallel and connected in series to the oscillation loop or between the oscillation loop and the ground, the phase circuit includes a first parallel circuit including a first coil and a capacitor, and the first parallel circuit is provided between the oscillation loop and the ground. And a second parallel circuit including a second coil and a resistor, one end of which is connected to the ground, and the first coil and the second coil are electromagnetically coupled to each other. 6. An F of the modulation circuit with respect to the phase circuit.
The modulator according to claim 1, wherein the ET switches are connected in parallel.