Measuring system for a probe

Abstract

A measuring system for probe, especially one for measuring dielectric properties and used in devices for measuring properties of dielectric constant changes in human or animal tissues, characterized in that it comprises a microwave resonance circuit (3) made on dielectric substrate and shaped in the form of a three-stage resonator composed of three segments of striplines with different impedances of each of the segments and arranged with respect to each other is such a way that successive segments are perpendicular to each other, and further comprises rows of grommets (2) with metallized surfaces connecting front surfaces on both sides of the substrate and constituting the earth of the probe.

Claims

1. A measuring system for a probe for measuring dielectric properties and used in a device for measuring properties of dielectric constant changes in human or animal tissues, the measuring system comprising: a microwave resonance circuit placed on a dielectric substrate, the microwave resonance circuit being shaped in the form of a three-stage resonator composed of three segments of striplines, the three segments including a first segment, a second segment, and a third segment, wherein the first segment, the second segment, and the third segment have different values of a complex impedance, the different values of the complex impedance being selected so that a resonance frequency in the range from 2.5 GHz to 3.5 GHz is obtained, wherein the three segments are arranged with respect to each other in such a way that (i) the first segment is connected with an output of the microwave resonance circuit, (ii) the first segment is connected to and perpendicular to the second segment, and (iii) the second segment is connected to and perpendicular to the third segment, wherein the measuring system further comprises rows of grommets with metallized surfaces connecting a first surface located on a first side of the dielectric substrate with a second surface on a second side of the dielectric substrate, the first surface and the second surface being on opposite sides of the dielectric substrate and constituting the probe's earth, wherein the dielectric substrate has the form of a circle, the microwave resonance circuit being located on the first surface of the dielectric substrate, and the grommets are arranged annularly around the microwave resonance circuit, wherein the measuring system is supplied with a microwave signal by means of a coaxial connector of an SMB type, and wherein the coaxial connector is mounted on the second side of the dielectric substrate in such a way that a sting of the coaxial connector is insulated from a copper coat and connected with the microwave resonance circuit located on the first side of the dielectric substrate.

2. The measuring system for probe according to claim 1, wherein the dielectric substrate is a polytetrafluoroethylene laminate.

3. The measuring system for probe according to claim 1, wherein the second surface, which is opposite to the first surface on which the microwave resonance circuit is located, is metallized, primarily with copper and secondarily with gold.

4. The measuring system for probe according to claim 1, wherein the three segments are arranged in a U shape with respect to the output of the microwave resonance circuit.

Description

(1) The subject of the present invention is shown in an example embodiment in figures, of which

(2) FIG. 1 shows the measuring system in a view from the side of the contact with tissue;

(3) FIG. 2 shows the arrangement of resonator striplines;

(4) FIG. 3 shows the resonance circuit with coaxial connector of SMB type in the side view;

(5) FIG. 4 shows, in the form of a graph, an example measured reflection coefficient characteristics of the microwave probe in contact with skin of a human forearm;

(6) FIG. 5 shows measured reflection coefficient characteristics of the microwave probe for different solutions of physiological salt with glucose (0 and 500 mg/dl) and described in the following.

(7) The measuring system was made on a circle of PTFE laminate constructed as the dielectric layer 5 with the following parameters: dielectric constant .sub.r=2.5, substrate thickness h=0.635 mm, dielectric loss angle tangent tg()=0.0001, and metallization layer 1 with copper thickness t=18 m. The measuring probe diameter is 30 mm. Surface 1A of dielectric layer 5 is completely coppered with layer of gold sputtered on it. From this side, the system is supplied with microwave signal by means of coaxial connector 4 of SMB type. The coaxial connector is mounted on the circle in such a way that its sting is insulated from the copper coat and connected with the microwave resonance circuit 3 located in the other side of the circle. Resonance circuit in the form of three-stage resonator is located centrally on the surface of contact with tissue and is made in the form of three segments of stripline.

(8) Each of the segments is characterized with different values of their complex impedances, modules and phases of which for segments 3A, 3B, and 3C are: Z.sub.0A=32.5 and .sub.A=53; Z.sub.0B=35 and .sub.B=58; and Z.sub.0C=31.5 and .sub.C=60, respectively, for the resonance frequency of 3.3 GHz.

(9) The earth of the system in the form of upper surface 1A and lower surface 1B of dielectric substrate 5 that are connected by means of metallized grommets 2. The number and location of grommets is of no importance from the point of view of the invention essence, whereas it is important that appropriately large number of grommets ensures connection of earthed surfaces on both sides of the measuring system.

(10) From the point of view of description of its electric properties, the probe with the measuring system is a one-port element. Such circuit is characterized with the reflection coefficient represented by S11 in matrix representation. The reflection coefficient value for the probe with the measuring system as described in the example embodiment remaining in contact with skin on forearm of a human is presented by the graph in FIG. 4 where the minimum reflection coefficient value of the circuit occurs for the frequency 2.3 GHz. On the other hand, differences depending on composition of the examined solution are plotted in FIG. 5. The characteristics representing variation of modulus of the reflection coefficientparameter |S11| as a function of microwave signal frequency change shows the resonance curve of the measuring probe resonance circuit.

(11) The probe measuring system is designed to be applied in non-invasive examination of blood sugar changes in humans and properties of dielectric constant changes in human or animal tissues.