JPS60177705A - Oscillator - Google Patents

Abstract

PURPOSE:To obtain an oscillator having the fixed amplitude characteristics as well as the satisfactory lineraity by using the surface acoustic wave elements having the same amplitude charcteristics and different output phases as the frequency selecting phase shift elements and providing a phase synthesizer for two signals having a phase difference and a differential amplifier for buffer into a positive feedback loop. CONSTITUTION:A surface acoustic wave element 1 has the same amplitude characteristics and two outputs 5 and 6 of different phase characteristics to an input 4. Such element 1 connects both outputs to a phase synthesizer 4 and then connects the output at one side of a differential amplifier 3 to the input of the original element 1 via the amplifier 3 having the balanced output after phase synthesization. Thus a positive feedback loop is formed. At the same time, an oscillation output is extracted by the output at the other side of the amplifier 3. A phase synthesizer 2 gives vector synthesization to plural input signals having different phases and serves as a phase shifter that can control the phase shift amount according to the level of the control signal given from a control input terminal 7. For the element 1, the comb-shaped electrodes 25-27 are usually provided crossing each other on a ZnO substrate, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an oscillator that can be frequency controlled or frequency modulated.

Conventional Structure and Problems Conventionally, as a frequency modulated oscillator, a variable capacitance diode or the like is used as a part of the frequency determining element of an oscillation circuit, and the oscillation frequency is modulated by a control signal. Although this kind of circuit has a simple i14 configuration, the oscillation frequency tends to change due to the temperature characteristics specific to the variable capacitance diode and fluctuations in the power supply that provides the reference bias, and the variation in the capacitance value of the variable capacitance diode tends to change. However, it has drawbacks such as frequency modulation sensitivity changes due to variations in capacitance change characteristics, and linearity of frequency variation is not very good. Furthermore, when attempting to configure an oscillator with a semiconductor integrated circuit, it is difficult to integrate a variable capacitance diode at the same time as the circuit, so it is necessary to add a FiJ' variable capacitance diode to the integrated circuit oscillator. Not only does it not solve the problem of variations in stability and sensitivity, but it also becomes economically expensive.

SUMMARY OF THE INVENTION It is an object of the invention to provide a frequency modulated oscillator suitable for semiconductor integrated circuits.

Structure of the Invention The present invention provides a surface acoustic wave element having two different output phases relative to input, a phase synthesizer that synthesizes a plurality of signals having different phases and controls a signal synthesis ratio, and a phase synthesizer having a balanced output. A dynamic multiplier [ij] is provided, the two outputs of the ifJ surface acoustic wave element are applied to the two input sides of the phase synthesizer, and one output of the differential multiplier +-1j is applied to the surface acoustic wave element. is connected to the input terminal of the differential amplifier r to form a positive feedback loop.
By configuring an oscillator that extracts the output from the other output side of the 2-channel generator, a highly stable oscillator with variable frequency OJ' can be realized without using a variable capacitance diode, and FM modulation with good linearity can be achieved. It can also be used as a vessel.

DESCRIPTION OF EMBODIMENTS FIG. 1 is a basic block diagram of the present invention, and FIG. 2 shows vibrations [IJ characteristics 9 and phase characteristics 10] of a surface acoustic wave element. 1 is a surface acoustic wave element having two outputs 5 and 6 with the same vibration E1j characteristic and different phase characteristics with respect to the input 4. Each output is connected to the phase synthesizer 4, and the output after phase synthesis is The difference with balanced output! One output of the differential amplifier rlj is connected to the input of the original surface acoustic wave element through the l1IJ amplifier IIJ amplifier 3 to form a positive feedback loop, and the other output of the differential amplifier 11J is connected to the input of the original surface acoustic wave element. The configuration is such that the output of one output is collected from the output. This phase synthesizer performs vector synthesis of a plurality of input signals having two different phases, and is a phase shifter whose phase shift amount can be adjusted by the level of the control signal applied from the control input terminal 7.

In the characteristics of the surface acoustic wave element shown in FIG. 2, a certain phase θ has an oscillation loop gain capable of oscillation and positive feedback. By making stable oscillation at the frequency rkf0 at the point of , and adjusting the phase shift by 02 from the maximum θ1 by the phase synthesizer 2 in the oscillation loop, the oscillation frequency changes by 12 degrees from the oscillation frequency I'if1, and the control input The signal will be frequency modulated.

Here, Δf-θ2-01 corresponds to the phase difference of the output of the surface acoustic wave element. Surface acoustic wave elements, which are frequency selection and 11-handed phase shifting elements, have the same amplitude rlJ characteristics, and it is easy to extract outputs with different phases, and the linearity of the phase characteristics is good, so as mentioned above, When the oscillator is configured, the oscillation I
It becomes an oscillator with constant J, wide frequency variable range, and good linearity. In addition, one output of the differential multiplier with balanced output is used as the oscillation loop output, and the other output is used as the oscillation output, so the oscillation loop is not easily affected by the load, so the frequency stability is also affected by the load. In good condition.

Figure 3 shows a block diagram of an oscillator with improved performance based on the oscillator with the basic configuration shown in Figure 1. Elements that serve the same role as in FIG. 1 are designated by the same numbers. In addition to the configuration shown in FIG. 1, the configuration shown in FIG.
, 6 and the two inputs of the phase synthesizer, if
Also, one output of the differential amplifier RLJ 3 and the surface acoustic wave element 1
An amplifier 13 is connected between the differential amplifier 3 and the 0 input 4, and an oscillation output is taken out from the other output of the differential amplifier 3 via an amplifier 14. The amount of attenuation of a normal surface acoustic wave element is large, and the amount of attenuation is large,
With this and the multiplier 11J, an oscillator with good C/H can be realized. In addition, since an oscillation loop is formed from the differential amplifier 3 through the amplifier 13 and the oscillation output is also output from the differential amplifier 3 through the amplifier 14, the buffer effect is is very large, has very high frequency stability depending on the load, and can produce high-level output.

FIG. 4 shows the main circuit configuration of the block diagram of FIG. 3, and shows the phase synthesis circuit in detail.

Elements exhibiting effects similar to those in Section 10 are indicated by the same reference numerals. 1 is a surface acoustic wave element having the characteristics shown in Fig. 2, and the outputs 6 and 6 have the same amplitude characteristics and a phase difference of Δ0-0.
This is an element with two different output phases of 1-02. 1
1.12 is a pre-intensifier IJ with the same characteristics, and is 0 from 11.
It is output with a phase of 1 and a phase of 02 from 12.

Here, the phase synthesis circuit section will be explained.

The signal with phase θ1 is applied to the base electrode of transistor Q1,
A signal of phase θ2 is applied to the base electrode of C2, and C3,
Since the ground capacitors C1 and C2 are connected to the respective bases of C4, it is the same as if signals with phases of -C1 and -C2 were added, respectively. Prefix adder 11j 11.1
'2 is configured in advance with a balanced output, and transistors Q1. The same effect can be obtained even if it is directly added to Q3, C2, and C4 in an equilibrium state. The emitter electrodes of Ql and C3 are commonly connected and connected to the collector electrode of C5, and the emitter electrodes of Q2 and C4 are commonly connected and connected to the collector electrode of C6. Q and Q have a 6 6 differential amplifier rjJ configuration, and each emitter electrode is connected to a current source 16. Furthermore, the collector electrodes of Ql and C2 are commonly connected, and the collector electrodes of C3 and C4 are also commonly connected, and are connected to the differential amplifier 3. With this kind of connection, the load resistor R1 receives a vector-combined signal from the inputs of -01 and -02, and the load resistor R2 receives a signal of +0.
1 and +θ2 inputs produce a vector-synthesized signal. The combined ratio is applied to differentially connected control transistors Q5 and C6. By the control signal from the control input terminal 7, Q1. Q 2 , Q 3 + Q 4
For example, R2 has Ql, C2
Considering the phase inversion of the input signal by (01~θ2
It is clear that a phase shift of "-π" occurs. Similarly, a phase debt of (-01 to -C2) ten pi appears in the horse. A balanced output in which the amount of phase shift of C1 to θ2 changes can be obtained through the switches R1 and R2.

The first effect of using such a circuit is that the surface acoustic wave element outputs two signals with different phases, and a phase shift circuit that adjusts the synthesis ratio of these two signals using a control signal is placed in the positive feedback loop. By providing a variable capacitance diode and performing frequency control, it is possible to perform frequency modulation without using a variable capacitance diode. The second effect is that by setting the input and output sides of the phase synthesizer to two phases, positive and negative, it becomes possible to connect the current paths in a complementary manner, which prevents signal components from leaking into the power supply and ground paths. This makes it possible to stably configure integrated circuits that tend to have high line impedances such as power supply and ground lines. That is, load resistance R1,
The current flowing through R2 is complementary no matter what the control input is, and by connecting them in common, power supply terminal 1
The six currents do not include any signal components. Also, Ql,
The emitter current of C3 and the emitter currents of C2 and C4 are also complementary to each other, and by connecting them in common, no signal current flows through the control transistors Q5 and C6. Therefore, the synthesis ratio can be controlled only by considering the direct current or modulation signal frequency.

FIG. 5 shows details of a specific embodiment of the invention.

Elements exhibiting effects similar to those described above are designated by similar symbols. In addition, the bias circuit is omitted in "Circuit Diagram" 2. Afi As mentioned above, the output terminal 6 of the surface acoustic wave element,
Two signals having a phase difference Δθ=θ1−C2−900 are taken out at 6 and input to the respective emitter electrodes of transistors Q7 and C8, which function as a common base amplifier by means of ground capacitors C7 and C8. Here, the input stage is of a base-grounded type because it is suitable for impedance matching with the surface acoustic wave element in the embodiment, and is not particularly limited.

The two signals with different phases applied to the input terminals 5 and 6 are amplified by a grounded base type preamplifier having exactly the same characteristics, and the phase difference between the output signals of the surface acoustic wave element is Δθ.
-θ1-θ2-90° is input as an unbalanced signal to the phase synthesizer via coupling capacitors C3 and C4. Then, due to the operation of the phase synthesizer described above, the load resistances R1 and R2
A balanced signal that allows a phase change of Δθ-90° is taken out, is amplified by 1-1 by a differential amplifier composed of transistors Q9 and Qlo, and is connected to a load resistor R13.
, FL+4 as a balanced signal. Then, the signal from one R13 is input to the base electrode of the transistor Q11 of the common emitter multiplier via the coupling capacitor C5, and from the collector electrode to the input side of the original surface acoustic wave element via the coupling capacitor C1□. connected to form a positive feedback loop and oscillate. Similarly, the signal from the other R14 is input to the base electrode of the transistor Q12 via the coupling capacitor C6, and the oscillation output is taken out from the collector electrode.

In order for the phase synthesis circuit to operate optimally, it is desirable that the amplitude of the synthesized output signal does not vary with the control signal, that is, with the output phase angle. This means that when C5 and C6 are in equilibrium, Ql.

The gains of C2, C3, and C4 may be 1/4 of the maximum gain (which occurs in an unbalanced state). At this time, the combined output is given by
Resistors R3, R4, R are connected to the emitter electrodes of 3 and C4, respectively.
6, R6 is connected. Further, the resistors R7 and R8 serve to adjust the degree of increase 1j of the differential amplifier by the transistors Q5 and C6, that is, they serve as modulation sensitivity. A matching circuit 19 with 18 surface acoustic wave elements is an output impedance matching circuit. 17 is a current source.

Also, regarding the value for ground pressure and combined guests, it is about 10 to 20PF when used in the VHF band (1 guest).
? Therefore, it is a value that can be realized even when integrated circuits are implemented.

Next, the surface acoustic wave element mentioned above will be explained.

FIG. 6 is a schematic diagram of a surface acoustic wave element used in the present invention, and generally -J-, K<<>-shaped interdigital electrodes 25, 26, and 27 made of a ZnO substrate or the like are provided to intersect with each other. . When an input signal is applied from the input terminals 20 and 21 (in this example, the terminal 20 on one side is grounded), it is transmitted as a surface wave through the input electrode 21 to the output electrodes 26 and 37, and a reliable force with a frequency around 10 is generated. terminals 22 and 23
More is recovered. If the distance between the electrode centers is set so that the one-cycle delay times τ1 and τ2 are set to appropriate values, two outputs at different power positions 1 with the same amplitude characteristics and different output phases can be obtained. It can be taken out. Unexploded Lee
) in the example f. -1451%b and retarder Δθ-=9
It is designed to be o0.

Effects of the Invention According to the present invention, 1) Surface acoustic wave elements having the same amplitude characteristics and different output phases are used as frequency selective shift (''() elements, and a phase synthesizer and buffer for two signals having a phase difference are used. By installing a differential amplifier in the positive feedback loop, the amplitude characteristics are constant, linearity is good, and stable FM with little frequency fluctuation even when directly in front.
It can be used as an oscillator or voltage controlled oscillator.

2) In addition to 1), by adding a preamplifier and an output amplifier, an FM oscillator with good C/N and a more stable frequency with respect to the load and voltage control can be created. It becomes a type oscillator.

3) An oscillator suitable for integrated circuits can be obtained by configuring a phase synthesis circuit in which all signal paths are complementary and balanced in terms of direct current.

4) In addition, it is possible to cover almost the entire range of the phase shift amount of the phase shift circuit by simply changing the polarity of the input signal of the phase synthesizer. In other words, the total amount of phase shift is 9.
0' and there are four combinations of polarity, so 360
0 Can cover the entire range.

It has many excellent effects such as:

[Brief explanation of the drawing]

Fig. 1 is a block configuration diagram showing an embodiment of the oscillator of the present invention, Fig. 2 is a surface acoustic wave element characteristic diagram, Fig. 3 is a plotter diagram of an oscillator with improved performance, and Fig. 4 is a plotter diagram of the oscillator with improved performance. FIG. 5 is a circuit diagram of the main part of the embodiment, FIG. 5 is a specific circuit diagram, and FIG. 6 is a schematic diagram of a surface acoustic wave element. 1...Surface acoustic wave element, 2... ...Phase synthesizer, 3...Differential amplifier RP, 11.12...
...0[1 position increaser, 13.14...Output increase I'
ll unit, Ql, Q2, Q3゜Q4...transistor for phase synthesis, Q6, Q6...transistor for phase 1 synthesis control. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2, j2, 51 Figure 3, 3

Claims (3)

[Claims] (1) A surface acoustic wave element with two different output phases relative to the input, a phase synthesizer that synthesizes multiple signals with different phases and controls the signal synthesis ratio, and a differential amplifier with a balanced output. the two outputs of the surface acoustic wave element to the two input sides of the phase synthesizer, and the differential amplifier rl
] One output of the device is connected to the input terminal of the surface acoustic wave element to form a positive feedback loop, and the output is taken out from the other output side of the n'fl differential multiplier. oscillator. (2) Between the two output terminals of the surface acoustic wave element and the two input terminals of the 1fJ phase synthesizer,
1" and one output of the differential amplifier 11J,
An amplifier is connected between the input terminal of the surface acoustic wave element described ifJ, and an amplifier rlj is connected from the other output of the differential amplifier.
2. The oscillator according to claim 1, wherein the output is taken out through a oscillator. (3) The phase synthesizer includes first and second transistors, third and fourth transistors whose emitters are commonly connected, and sixth and sixth transistors whose emitters are commonly connected and which are differentially connected. the collectors of the first and third transistors and the collectors of the second and fourth transistors are respectively commonly connected; the emitters of the first and second transistors and the third and fourth transistors are connected in common; The emitter is connected to each collector of the fifth and sixth transistors, the base pair of the first and second transistors and the base pair of the third and fourth transistors are used as phase synthesis inputs, and A control value for the phase synthesis ratio is given to the base of at least one of the fifth and sixth transistors, and the balanced 2. The oscillator according to claim 1, wherein the oscillator is configured to obtain a phase composite signal of .