JPS59105565A - Electric field detecting circuit - Google Patents

Abstract

PURPOSE:To contrive to enlarge the dynamic range of an electric field detecting circuit, by comparing detection output voltage corresponding to the electric field passing through a voltage shift circuit with reference voltage to subject an input variable attenuator and the voltage shift circuit to feed-back control. CONSTITUTION:The electric field detection signal passing a variable attenuator 3 comes to electric field detection output voltage good in linearity through a logarithm amplifier 1, a detector circuit 2 and a voltage shift circuit 6. On the other hand, this detection output voltage is compared to reference voltage by a comparator 5 to subject the attenuator 3 and the circuit 6 to feed-back control through a memory circuit 4 for temporarily storing the comparison result and electric field detection good in linearity is performed without using a multi- stage logarithmic amplifier circuit to make it possible to attain to enlarge the dynamic range of an electric field detecting circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electric field detection circuit inserted into communication equipment, measuring instruments, etc. to obtain electric field information.

Conventionally, this type of electric field detection circuit includes a logarithmic amplifier that logarithmically amplifies an input signal and a detection circuit that detects the output of the logarithmic amplifier. By connecting these logarithmic amplifiers in multiple stages, the linearity of the logarithmic characteristics of this logarithmic amplifier has been improved. However, this multi-stage connection tends to cause abnormal oscillation when the input signal frequency becomes high, so there is a limit to the number of connections. , and the dynamic range had to be below a certain level.

SUMMARY OF THE INVENTION An object of the present invention is to provide an electric field detection circuit that can eliminate such conventional drawbacks and greatly expand the dynamic range.

The electric field detection circuit of the present invention includes a variable attenuator that attenuates an input signal using a first control signal, an amplifier that amplifies the output of the variable attenuator, and a detector that detects the output of the amplifier and outputs a DC voltage. a voltage circuit that shifts the output voltage of this detector by a second control signal, a comparison circuit that compares all output voltages of this voltage shift circuit with a predetermined reference voltage, and a temporary memory for the output of this comparison circuit. A memory circuit that
It is configured to include a control means for controlling the variable attenuator and the voltage shift circuit in a step-by-step manner by respectively controlling the first and second control signals L11i based on the output of the storage circuit.

The present invention will be explained in detail below with reference to the drawings.

FIG. 1 is a block diagram of a conventional electric field detection circuit, which is constructed by connecting a logarithmic amplifier 1 and a filter circuit 2 in cascade. FIG. 3 ta+ shows its input/output characteristic diagram.

That is, when the input signal level is B (dBμ), the output signal level is I) (vl), and when C (dRμ), it is E (v), and the output signal is nearer to the input signal change amount FdB (=C-By). The range was E-1)(vl).

FIG. 2 is a block diagram of an electric field detection circuit according to an embodiment of the present invention), and a case will be described in which settings are made to obtain a dynamic range 92 times that of the conventional circuit. First, the input signal is applied to the logarithmic amplifier 1 after passing through the variable attenuator 3, but the initial state of the variable attenuator 3 is set to zero. The output of this logarithmic amplifier l is applied to a detection circuit 2, where it is converted into a DC voltage. This DC normal pressure is applied to the voltage shift circuit 6, and this voltage shift circuit 6 is one of them! Voltage foot circuit 6
The initial state setting voltage 'kO (Vl) is assumed to be 'kO (Vl).

On the other hand, the output of the voltage shift circuit 6 is connected to a comparator (comparison D
o path) joins 5. The reference voltage L of this comparator 5 (
v) is the output signal level E (set to vl) when the input signal level C (dBμ) just before the logarithmic amplifier l reaches the saturation region is detected by the detection circuit 2. It is stored using the output information of the comparator 5. The variable attenuator 3 is controlled so that the output of the circuit 4 becomes a predetermined attenuation amount F' (dB), and at the same time, the set voltage of the voltage/foot circuit 6 is controlled from 't-0 (Vl to F(v)). , the input signal level is C
(dBμ), the output of the detection circuit 2 has the same characteristics as the conventional one as shown in FIG. 3 (bl), but the output of the voltage soft circuit 6 shows the voltage E
(v), and a logarithmic characteristic with a wide dynamic range as shown in FIG. 3(c) is obtained.

As is clear from the description of this embodiment, in the conventional electric field detection circuit, the amount of change in the output signal that is linear with respect to the amount of change in the input signal F (dB) (=C-B) is only E - D (vl). However, in this example, the input signal change amount is 2F (dB) (*H-
The amount of linear output signal change with respect to B) is GD(-i=
2(E-D))(V), resulting in approximately twice the dynamic range.

Although this embodiment has been described as an example in which the dynamic range is doubled, a comparator 5 is further added to make it possible to further vary the attenuation amount of the variable attenuator 3 and the set voltage of the voltage shift circuit 6. By doing so, the dynamic range can be further widened by the output information of the memory circuit 4.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a conventional electric field detection circuit, Fig. 2 is a block diagram of an embodiment of the present invention, Fig. 3 (al is an input/output characteristic diagram of a conventional electric field detection circuit, Fig. 3(b) is an input/output characteristic diagram of the detection circuit of this embodiment, and FIG. 3 (C1 is an input/output characteristic diagram of the entire embodiment of this embodiment.) ...detection circuit,
3...variable attenuator, 4...memory circuit,
6: Comparator, 6: Voltage shift circuit. 6--2 input 'Yu No. dBIL) □
λno] Shi No. Level (df$) (α)
(4) Figure 3 → ^Qap? nirehe)L/(dBF,)(C)

Claims (1)

[Claims] a voltage shift circuit that shifts the output voltage of the detector according to a second control signal, and compares the output voltage of the voltage shift circuit with a predetermined reference voltage. a comparator circuit; a memory circuit for temporarily storing the output of the comparator circuit; and a memory circuit for forming the first and second control signals, respectively, from the outputs of the memory circuit and controlling the variable attenuator and the voltage shift circuit in stages. and a control means for controlling the electric field detection circuit.