JPH02306706A - Surface acoustic wave oscillator - Google Patents

Abstract

PURPOSE:To measure the open loop characteristic accurately while the impedance is matched by breaking an oscillation loop, providing a test terminal to both broken points respectively, providing an impedance matching circuit respectively between each test terminal and the oscillation loop and connecting both the test terminals with a jumper. CONSTITUTION:A part of an oscillation loop is broken and test terminals 6a, 6b are provided to both ends of the broken part respectively and impedance matching circuits 7a, 7b to be matched with the impedance of the measuring instrument connecting to the test terminals 6a, 6b between the test terminals 6a, 6b and the oscillating loop respectively. Then both the test terminals 6a, 6b are connected by a jumper 8. Thus, when it is required to measure the open loop characteristic, the jumper 8 is removed to connect the measuring instrument of a prescribed impedance is connected to the test terminals 6a, 6b. Thus, the open loop characteristic is measured accurately while the impedance is matched.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a surface acoustic wave oscillator using a surface acoustic wave device.

[Prior Art] A typical conventional example of this type of surface acoustic wave oscillator is shown in FIG.

That is, in this oscillator, the amplifier 2, surface acoustic wave device 3, and phase shifter 4 are connected in a loop to form an oscillation loop. A capacitor 5, a directional coupler, etc. are used to take out the output.

As the surface acoustic wave device 3, for example, a two-boat type surface acoustic wave resonator or a surface acoustic wave delay line is used.

The phase shifter 4 is for adjusting the phase of the oscillation loop to satisfy the oscillation conditions, and is of a voltage control type including, for example, a variable capacitance diode, and as in this example, it is controlled by the control voltage Vt. The oscillation frequency of the oscillator may be changed, that is, the oscillator may be a voltage controlled oscillator (VCO).

[Problem to be solved by the invention]

If you want to investigate the open-loop characteristics of a conventional surface acoustic wave oscillator like the one above, cut one of the points A-C in the diagram and connect a measuring device such as a network analyzer to both ends. Must.

However, the impedance at the point of cut is generally the impedance of the measuring instrument (usually 50Ω or 75Ω).
Ω), so the open-loop characteristics must be evaluated in a mismatched state.

In this mismatched state, there is a high possibility that characteristics (eg, gain and phase) will be exhibited that are far from the original open-loop characteristics, and therefore, there is a problem that the characteristics cannot be measured accurately.

As a result, for example, when mass producing surface acoustic wave oscillators, it is necessary to check the open-loop characteristics of the product during or after production, and the discovery of the cause of the defect is delayed due to incorrect measurement data caused by impedance mismatching. , it may worsen the product yield.

Therefore, the main object of the present invention is to provide a surface acoustic wave oscillator that enables accurate measurement of interloop characteristics with impedance matching.

[Means to solve the problem]

In order to achieve the above object, the surface acoustic wave oscillator of the present invention divides the oscillation loop, provides test terminals on both sides of the divided portion, and provides impedance matching circuits between each test terminal and the oscillation loop. , and both test terminals are connected with a jumper.

[Effect]

Normally, if you connect the jumper as shown above,
Since an oscillation loop is formed, oscillation is possible.

If you need to measure open loop, just remove the jumper and connect the meter to the test terminal. In that case,
Each impedance matching circuit allows the impedance at each test terminal to be matched to the measuring instrument used, thereby allowing the open loop characteristics to be accurately measured with impedance matching.

【Example〕

FIG. 1 is a block diagram showing a surface acoustic wave oscillator according to an embodiment of the present invention. Components equivalent to those in the example of FIG. 4 are given the same reference numerals, and the differences from the conventional example will be mainly explained below.

In this embodiment, one part of the oscillation loop (corresponding to point B in FIG. 4) is divided, and test terminals 6a and 6b are provided on both sides of the part, and each test terminal 6a and 6b is Test terminals 6a and 6b are connected between the oscillation loops.
Impedance matching circuits 7a and 7b are respectively provided for matching the impedance of the measuring instrument connected to the
A jumper 8 connects both test terminals 6a and 6b.

For example, a π match circuit can be used as each impedance matching circuit 7a, 7b. This is a matching circuit that can convert from a higher impedance to a lower impedance and vice versa, and a specific example thereof is shown in FIG.

In this example, if the characteristic impedance of the measuring device such as a network analyzer connected to the test terminals 6a and 6b is, for example, 50Ω (the concept is the same even in the case of 75Ω), the output impedance of the phase shifter 4 is, for example, 50Ω.
If it is higher than Ω, if CIm<CzA is selected in the impedance matching circuit 7a, the impedance is converted from the higher one to the lower one, and an impedance matching circuit is established on the test terminal 6a side. Furthermore, when the surface acoustic wave device 3 has an impedance higher than 50Ω, impedance matching on the test terminal 6b side can be achieved by selecting CIm<Czm in the impedance matching circuit 7b. In this embodiment, the impedance at the test terminals 6a and 6b is matched with the impedance of the measuring instrument.

In such a surface acoustic wave oscillator, normally, if jumper 8 is connected between test terminals 6a and 6b,
Since an oscillation loop is formed, oscillation is possible.

When you need to measure open loop characteristics, jumper 8
It is sufficient to disconnect the test terminals 6a and 6b and connect a measuring device with a predetermined impedance to the test terminals 6a and 6b. FIG. 3 shows an example in which a network analyzer 9 is connected. Checkpoints in this case are, for example, (1) whether the gain is 1 or more at the desired oscillation frequency, and (2) whether the phase is an integral multiple of 360° at the desired oscillation frequency.

With the above method, the open loop characteristics can be measured with the impedances matched, so that the measurement can be performed accurately.

As a result, for example, when mass producing surface acoustic wave oscillators, ■
By investigating the open-loop characteristics of surface acoustic wave oscillators that do not oscillate or oscillate but oscillate abnormally, the cause of the failure can be quickly found and countermeasures can be taken quickly.
Furthermore, after measurement, oscillation is enabled by reconnecting jumper 8, so the characteristics can be measured non-destructively. ■Characteristics can be checked at an intermediate stage of manufacturing (after the oscillation loop is formed); Because it can be performed accurately, it is easy to identify defects in the amplifier 2, surface acoustic wave device 3, phase shifter 4, etc.
(In some cases, it may be possible to find out if there is an abnormality in the rotation.), By checking the open loop characteristics, adjust the internal phase shifter 4 for all blocks so that the loop has an optimal phase relationship (integer multiple of 360° within the loop). It is possible to improve the yield of products by, for example, taking the following factors into account.

The test terminals 6a, 6b, impedance matching circuits 7a, 7b, etc. as described above may be provided at locations corresponding to points A and 0 in FIG. 4, in addition to the locations shown in FIG.

〔Effect of the invention〕

As described above, according to the surface acoustic wave oscillator of the present invention, its open-loop characteristics can be accurately measured with impedance matching.

As a result, for example, during mass production of surface acoustic wave oscillators, it is now possible to easily and accurately perform adjustments and corrections to products after manufacture, as well as intermediate checks during manufacture, thereby improving product yield. I can do it.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a surface acoustic wave oscillator according to an embodiment of the present invention. FIG. 2 is a circuit diagram showing a specific example of the impedance matching circuit in FIG. 1. FIG. 3 is a diagram showing a state in which a network analyzer is connected to the surface acoustic wave oscillator of FIG. 1 to measure open loop characteristics. FIG. 4 is a block diagram showing an example of a conventional surface acoustic wave oscillator. 2...Amplifier, 3...Surface acoustic wave device, 4...
- Phase shifter, 6a, 6b...Test terminal, 7a. 7b... Impedance matching circuit, 801. jumper.

Claims (1)

[Claims] (1) In a surface acoustic wave oscillator in which an oscillation loop is formed by connecting at least an amplifier, a surface acoustic wave device, and a phase shifter in a loop, the oscillation loop is divided and test terminals are connected on both sides of the divided point. A surface acoustic wave oscillator characterized in that an impedance matching circuit is provided between each test terminal and the oscillation loop, and both test terminals are connected with a jumper.