JP3154154B2 - Parallel T-type high-frequency bridge device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a parallel T-type high-frequency bridge device configured to continuously and automatically perform a balancing operation and a detection of a balance capacity of a parallel T-type high-frequency bridge circuit.

[0002]

2. Description of the Related Art In the illustration of a parallel T-type high-frequency bridge circuit shown in FIG. 3, the balance is determined by the vector sum of output currents I1 and I2 of two T-type circuits, that is, the bridge output current I.
The variable capacitors C3 and C3 of each T-type circuit are set so that o becomes zero.
6 is adjusted. In a conventional device using a parallel T-type bridge circuit, regardless of the type of variable capacitance and the adjustment means therefor, in the process of balancing, the bridge output current Io is detected so that Io becomes zero. An operation for adjusting the two variable capacitors C3 and C6 was required.

[0003]

Therefore, the conventional parallel T
In the balancing operation of the high-frequency high-frequency bridge device, it is necessary to adjust the variable capacitance of the two sides while detecting the output current Io of the bridge every time the measurement sample changes, so that it is difficult to measure a sample that changes continuously. In addition, automation of the measurement required a complicated balancing device such as a servo mechanism. An object of the present invention is to solve such a problem and to provide a parallel T-type high-frequency bridge device capable of continuously and automatically measuring a sample with a simple configuration.

[0004]

A parallel T-type high-frequency bridge circuit using variable capacitance diodes on two variable capacitance sides and a cycle for sweeping the capacitances of the diodes on the two variable capacitance sides with a predetermined cycle difference. A capacitance sweep circuit that outputs two different types of sweep waves, a detection circuit that detects a change in the amplitude of the bridge output current due to a periodic sweep of the capacitance, a peak detection circuit that detects an equilibrium time point based on the change in the amplitude of the detection output, A sample-and-hold circuit that samples and outputs a capacitance sweep wave based on a balanced timing signal output from a detection circuit, a variable capacitance diode having a pair characteristic with a variable capacitance diode of a bridge circuit, and a bridge to which the sampling wave to be sampled is applied. Apply the output of the sample and hold circuit to the variable capacitance diode of the circuit and the variable capacitance diode of the pair characteristic. Those consisting of a capacitance detecting circuit for detecting and outputting a capacity when.

[0005]

[Operation] If the capacitances of the variable capacitance diodes on the two variable capacitance sides of the parallel T-type high-frequency bridge circuit are cycle-swept by sweep waves having a sufficiently large cycle difference, respectively, the longer sweep cycle can be performed within one cycle. , The point where the capacitance of the diodes on both sides satisfies or approximately satisfies the bridge equilibrium condition. The bridge output current is subjected to amplitude modulation in accordance with the capacitance sweep of the diode, and a curve connecting the valleys of the amplitude of the amplitude-modulated wave during one of the longer sweep periods indicates the balance process of the bridge. . Therefore, if the bridge output current is detected and the portion where the curve approaches the zero level is taken out, a waveform output in which the equilibrium point comes to the maximum amplitude point can be obtained. By sampling the capacitance sweep wave with the balanced timing signal output at the time of the maximum amplitude, the obtained voltage is
When the capacitance is applied to the variable capacitance diode whose capacitance is being swept by the capacitance-swept wave and the variable capacitance diode having a pair characteristic, and the capacitance at that time is detected, the equilibrium capacitance can be known indirectly.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, variable capacitance diodes 1a and 1b are used on two variable capacitance sides of a parallel T-type high frequency bridge circuit 1 driven by a high frequency power supply 1c. From the terminal 31 of the capacitance sweep circuit 3, a sawtooth wave A having a period T is outputted,
Are output, and each output is the sample 1e
Applied to the variable capacitance diodes 1a and 1b via a changeover switch 2 for applying a sawtooth wave A having a period T to the variable capacitance diode whose capacitance needs to be detected in accordance with the measurement of the real and imaginary components of Have been. Thereby, 1a, 1
(b) The capacitance of both diodes is swept, and a combination of the number of capacitance values corresponding to the difference between the sweep periods of both diodes is obtained during the sweep period T. Therefore, if the sweep range of the capacitance is adjusted to the measurement range of the sample 1e, a combination of capacitance values that satisfies or approximately satisfies the bridge equilibrium condition exists during the sweep period T. The bridge output current Io is subjected to amplitude modulation in accordance with the sweep of the capacitance of the diode, and an amplitude modulation wave F is output by the current detector 1d. A pair of curves E connecting the valleys of the amplitude of the output show the equilibrium process of the bridge. The output of the current detector 1d is amplified to a required size by the amplifier circuit 4, and the detection circuit 5 extracts a portion where the curve E approaches the zero level most. This detection output G is a pulse train having a part of the curve E as an envelope, and the point of the maximum amplitude is the equilibrium point of the bridge. Next, the detection output amplified to a required size by the amplification circuit 6 is input to the peak detection circuit 7, and a maximum amplitude point is detected to generate a balanced timing pulse H, which is used as a sampling signal and is used as a sample-and-hold signal. The circuit 8 samples the sawtooth wave output of the terminal 31 of the capacitance sweep circuit 3. This sampling output is supplied to the variable capacitance diodes 1 a and 1
b is applied to each of the variable capacitance diodes 9a and 9b having a pair characteristic, and the variable capacitance diode 9a and 9b having a pair T and a variable capacitance diode on the bridge side whose capacitance is being swept by the sawtooth wave output. A capacitance diode is selected. The capacitance detection circuit 9 detects the capacitance of the variable capacitance diode 9a or 9b during the application of the sampling output, and when the capacitance is 9a, the imaginary component of the sample 1e, and when the capacitance is 9b, the real component, , Respectively.

[0007]

As described above, the present invention has the above-described structure. Since the balance is periodically obtained with the capacitance sweep of the variable capacitance diode on the bridge side, and no special balancing operation is required, the measurement of the sample is performed. Can be performed continuously and automatically and quickly, and the measurement value can be read directly at the indicator.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of a parallel T-type high-frequency bridge device of the present invention.

FIG. 2 is a waveform chart of the embodiment of the present invention shown in FIG.

FIG. 3 is an explanatory diagram of a parallel T-type high-frequency bridge circuit.

[Description of sign]

 DESCRIPTION OF SYMBOLS 1 Parallel T-type high frequency bridge circuit 1a, 1b Variable capacitance diode 1c High frequency power supply 1d Current detector 1e Sample Io Bridge output current 2 Changeover switch 3 Capacitance sweep circuit 31 Saw cutting wave output terminal 32 Triangular wave output terminal 4 Amplifier circuit 5 Detection circuit 6 Amplification circuit 7 Peak detection circuit 8 Sample hold circuit 9 Capacitance detection circuit 9a 1a and variable capacitance diode 9a and 1b and variable capacitance diode with pair characteristic 10 Indicators A, B, F, G, H and V

Claims (1)

(57) [Claims] 1. A parallel T-type high-frequency bridge circuit using a variable capacitance diode as a variable capacitance on two variable capacitance sides,
A capacitance sweep circuit that outputs a capacitance sweep wave for periodically sweeping the capacitance of the variable capacitance diodes on the two variable capacitance sides with a predetermined period difference, and detection for detecting an amplitude change of a bridge output current accompanying the period sweep of the capacitance; A circuit, a peak detection circuit for detecting the balance point of the bridge from the output of the detection circuit,
A sample-and-hold circuit that samples and outputs a capacitance sweep wave of the variable capacitance diode based on an output signal of the peak detection circuit; a variable capacitance diode having a pair characteristic with the variable capacitance diode; A parallel T-type high-frequency bridge device comprising: a capacitance detection circuit that detects and outputs a capacitance when an output of the hold circuit is applied.