NICKEL ZINC COPPER FERRITE FOR VUHF ANTENNA APPLICATION

Abstract

A composition and a solid material is especially suitable for the manufacture of an antenna adapted to operate in the very high frequency and ultra high frequency or V/UHF band. The composition has the formula Ni.sub.aZn.sub.bCu.sub.cCo.sub.dFe.sub.2-δO.sub.4, in which 2(a+b+c+d)+3(2−δ)=8, 0.05<b<0.5, e.g. 0.1<b<0.5, e.g. 0.1<b<0.4, e.g. 0.15<b<0.35, 0.10<c<0.25, preferably 0.15<c<0.25, alternatively c is 0.20, 0.04<d<0.25, preferably 0.06<d<0.25, and more preferably 0.07<d<0.25, and δ<0.05.

Claims

1. A composition of the formula Ni.sub.aZn.sub.bCu.sub.cCo.sub.dFe.sub.2-δO.sub.4, wherein: 2(a+b+c+d)+3(2−δ)=8 0.05<b<0.5, 0.10<c<0.25, 0.04<d<0.25, and δ<0.05.

2. The composition according to claim 1, having a Ni/Zn ratio of 1 to 15.

3. The composition according to claim 1, wherein the composition has a spinel structure.

4. The composition according to claim 1, wherein the composition is chosen from compositions of the following formulas:
Ni.sub.0.4805Zn.sub.0.3195Cu.sub.0.20Co.sub.0.06Fe.sub.1.96O.sub.4,
Ni.sub.0.4405Zn.sub.0.3195Cu.sub.0.20Co.sub.0.10Fe.sub.1.96O.sub.4,
Ni.sub.0.4347Zn.sub.0.3153Cu.sub.0.20Co.sub.0.11Fe.sub.1.96O.sub.4,
Ni.sub.0.4231Zn.sub.0.3069Cu.sub.0.20Co.sub.0.13Fe.sub.1.96O.sub.4,
Ni.sub.0.4115Zn.sub.0.2985Cu.sub.0.20Co.sub.0.15Fe.sub.1.96O.sub.4; and
Ni.sub.0.6Zn.sub.0.2Cu.sub.0.20Co.sub.0.06Fe.sub.1.96O.sub.4.

5. A solid material having a composition as defined according to claim 1.

6. The solid material according to claim 5, forming a magneto-dielectric material.

7. The solid material of claim 5, wherein it has a magnetic permeability μ′ of 10 to 20 for the VHF range (1 MHz to 300 MHz) or μ′ of 5 to 15 for the V/UHF range (200 MHz to 600 MHz).

8. The solid material according to claim 5, wherein it has magnetic losses tan(δ.sub.μ)<0.06.

9. A VHF or V/UHF antenna wherein it comprises a composition according to claim 1.

10. The VHF or V/UHF antenna of the printed or microstrip type, wherein it comprises one or more layers of a substrate bonded to a radiating element, of which one or more layers of the substrate comprises a composition according to claim 1.

11. The VHF or V/UHF antenna according to claim 9, wherein it has a larger dimension of less than 300 mm.

12. A method for manufacturing a composition according to claim 1, characterised in that said method comprises: grinding the raw materials providing Ni, Zn, Cu, Co, Fe and O, typically NiO; ZnO; CuO; Co.sub.3O.sub.4 and Fe.sub.2O.sub.3, after grinding, the powder is dried and then sieved, after sieving, the powder is heat-treated, after heat treatment, the powder undergoes a second grinding, for then the powder is shaped into a solid material.

13. The method according to claim 12, wherein prior to shaping, the method comprises coating the powder with a binder to provide a shaped material.

14. The method according to claim 12, wherein after shaping the method comprises sintering the shaped material.

15. The composition of claim 1, wherein: 0.15<b<0.35 0.15<c<0.25, and alternatively c is 0.20, 0.07<d<0.25, and δ<0.05.

16. The solid material of claim 5, having a magnetic permeability μ′>1 and a dielectric permittivity ε′>1.

17. The solid material of claim 5, wherein μ′≥5 and ε′≥10.

18. The solid material according to claim 5, wherein the dielectric losses tan(δ.sub.ε) <0.02 over the frequency band between 100 and 200 MHz.

Description

[0110] In the figures:

[0111] FIG. 1 is a graph showing the magnetic permeability and magnetic losses of a conventional nickel zinc ferrite (NZ50 where Ni/Zn is 1.77 and Co is 0.008) and a nickel zinc copper ferrite (Ni.sub.0.5005Zn.sub.0.3195Cu.sub.0.20Co.sub.0.04Fe.sub.1.96O.sub.4 where Ni/Zn is 1.57 and Co is 0.04) against frequency.

[0112] FIG. 2 is a graph showing the magnetic permeability and magnetic losses of NZC ferrites against frequency. Ni.sub.0.5005Zn.sub.0.3195Cu.sub.0.20Co.sub.0.04Fe.sub.1.96O.sub.4 (Ni/Zn is 1.57 and Co is 0.04) and Ni.sub.0.4805Zn.sub.0.3195Cu.sub.0.20Co.sub.0.04Fe.sub.1.96O.sub.4(Ni/Zn is 1.50 and Co is 0.06).

[0113] FIG. 3 is a graph showing the magnetic permeability and magnetic losses of NZC ferrites as a function of frequency, where Ni.sub.0.4805Zn.sub.0.3195Cu.sub.0.20Co.sub.0.04Fe.sub.1.96O.sub.4 (Ni/Zn is 1.50 and Co is 0.06); Ni.sub.0.4405Zn.sub.0.3195Cu.sub.0.20Co.sub.0.10Fe.sub.1.96O.sub.4(Ni/Zn is 1.38 and Co is 0.1) and Ni.sub.0.6Zn.sub.0.2Cu.sub.0.20Co.sub.0.06Fe.sub.1.96O.sub.4 (Ni/Zn is 3 and Co is 0.06).

[0114] FIG. 4 is a graph showing the magnetic permeability and magnetic losses of NZC ferrites as a function of frequency, where Ni.sub.0.4347Zn.sub.0.3153Cu.sub.0.20Co.sub.0.11Fe.sub.1.96O.sub.4 (Ni/Zn is 1.38 and Co is 0.11); Ni.sub.0.4231Zn.sub.0.3069Cu.sub.0.20Co.sub.0.13Fe.sub.1.96O.sub.4(Ni/Zn is 1.38 and Co is 0.13) and Ni.sub.0.4115Zn.sub.0.2985Cu.sub.0.20Co.sub.0.15Fe.sub.1.96O.sub.4 (Ni/Zn is 1.38 and Co is 0.15).

[0115] FIG. 5 is a graph showing the magnetic permeability and magnetic losses of the material Ni.sub.0.4405Zn.sub.0.3195Cu.sub.0.20Co.sub.0.10Fe.sub.1.96O.sub.4 as a function of frequency.

[0116] FIG. 6 is a graph showing the magnetic permeability and magnetic losses of the material Ni.sub.0.6Zn.sub.0.2Cu.sub.0.20Co.sub.0.06Fe.sub.1.96O.sub.4 as a function of frequency.

[0117] FIG. 7 is a graph showing the permittivity and dielectric losses of the material Ni.sub.0.4405Zn.sub.0.3195Cu.sub.0.20Co.sub.0.10Fe.sub.1.96O.sub.4 as a function of frequency.

[0118] FIG. 8 is a graph showing the permittivity and dielectric losses of the material Ni.sub.0.6Zn.sub.0.2Cu.sub.0.20Co.sub.0.06Fe.sub.1.96O.sub.4 as a function of frequency.

EXAMPLES

[0119] To evaluate the potential of the materials according to the invention, we are mainly interested in the change in the permeability and the magnetic losses as a function of frequency. This means looking at the moment when the losses increase (which coincides with the onset of ferromagnetic resonance) and the value of the permeability before resonance.

[0120] Measurements of permeability, permittivity, magnetic and dielectric losses are carried out between 1 MHz and 1 GHz using a HP4291A impedance analyser.

[0121] For the measurement of permeability and magnetic losses, samples in the form of a cylindrical as-sintered torus type APC7 are manufactured (Ø.sub.ext≤7 mm; Ø.sub.int≥3.05 mm; thickness ≤3 mm). Measurements are made in the Keysight 16454A Magnetic Material Test Fixture. The references for this measure can be found on the manufacturer's website (reference document: 16454A Magnetic Material Test Fixture Operation and Service Manual and Materials Measurement: Magnetic Materials—Application Brief at https://www.keysight.com/en/pd-1000000509%3Aepsg %3Apro-pn-16454A/magnetic-material-test-fixture?μm-PL&nid=−536902475.536879639&cc-FR&Ic-fre).

[0122] For the measurement of permittivity and dielectric loss, samples in the form of a 10 mm square plate of varying thickness (1; 0.5; 0.3 mm) are manufactured. Capacitance and loss factor are then measured in the impedance analyser (HP4291A) using the HP Agilent Keysight 160924 Spring Clip Test Fixture allowing for measurement between 1 and 500 MHz.

[0123] FIG. 1 shows such curves. The dotted line shows a classic spinel ferrite (NZ50, marketed by EXXELIA) and the appearance of the resonance can be observed before 50 MHz (permeability peak at about 20 MHz). The losses increase and make the material unusable as VHF and/or UHF antenna material. The use of a nickel-zinc-copper ferrite with a copper content of 0.2 as shown in FIG. 1 (Ni.sub.0.5005Zn.sub.0.3195Cu.sub.0.20Co.sub.0.04Fe.sub.1.96O.sub.4) allows the resonance to be shifted to higher frequencies, above 50 MHz (peak at about 100 MHz).

[0124] FIG. 2 shows the composition Ni.sub.0.4805Zn.sub.0.3195Cu.sub.0.20Co.sub.0.06Fe.sub.1.96O.sub.4. With a Ni/Zn ratio of 1.5 and an increased cobalt content of 0.06, the resonance is pushed to a higher frequency, allowing low losses (tan δ.sub.μ<0.04) up to 100 MHz. This gives a material that can be used as an antenna material between 1 and 100 MHz with a μ′ around 29.

[0125] FIG. 3 compares two new materials to the one already shown in thin solid line/grey in FIG. 2 (Ni.sub.0.4805Zn.sub.0.3195Cu.sub.0.20Co.sub.0.06Fe.sub.1.96O.sub.4). The first material shown in thick solid line/black has the following composition: Ni.sub.0.4405Zn.sub.0.3195Cu.sub.0.20Co.sub.0.10Fe.sub.1.96O.sub.4. In comparison, the Ni/Zn ratio was slightly decreased (due to the fact that the strong addition of cobalt was done by substitution of nickel) but the proportion of cobalt was strongly increased to 0.1 mol. This shows the direct effect of the cobalt in pushing back the resonance after 200 MHz. The similar effect is observed on the material shown as a dotted line in FIG. 3: Ni.sub.0.6Zn.sub.0.2Cu.sub.0.20Co.sub.0.06Fe.sub.1.96O.sub.4. Compared to the material shown in thin/grey solid line, the cobalt content remained the same but the Ni/Zn ratio was doubled. It can be seen that the resonance is also pushed back after 200 MHz.

[0126] FIG. 4 shows three compositions (Ni.sub.0.4347Zn.sub.0.3153Cu.sub.0.20Co.sub.0.11Fe.sub.1.96O.sub.4; Ni.sub.0.4231Zn.sub.0.3069Cu.sub.0.20Co.sub.0.13Fe.sub.1.96O.sub.4; and Ni.sub.0.4115Zn.sub.0.2985Cu.sub.0.20Co.sub.0.15Fe.sub.1.96O.sub.4), each with a Ni/Zn ratio set at 1.38. The cobalt content of these compositions is set at 0.11, 0.13 and 0.15 respectively. The effect of the cobalt can be clearly seen, allowing the material to be used at higher frequencies (above 300 MHz for the composition with a cobalt content of 0.15).

[0127] FIGS. 5 and 6 focus on the frequency range between 100 and 200 MHz. This frequency band is of great interest because of the many VHF applications operating in this range and in particular for aeronautical applications (band of use between 118 and 156 MHz and more particularly between 118 and 137 MHz for aeronautical traffic). Over these particular frequency bands it is observed in FIGS. 4 and 5 that the materials Ni.sub.0.4405Zn.sub.0.3195Cu.sub.0.20Co.sub.0.10Fe.sub.1.96O.sub.4 et Ni.sub.0.6Zn.sub.0.2Cu.sub.0.20Co.sub.0.06Fe.sub.1.96O.sub.4 show advantageous performance with magnetic losses tan(δ.sub.μ)<0.02 and a magnetic permeability μ′ 15

[0128] FIGS. 7 and 8 show the relative permittivity and dielectric losses of the materials Ni.sub.0.4405Zn.sub.0.3195Cu.sub.0.20Co.sub.0.10Fe.sub.1.96O.sub.4 and Ni.sub.0.6Zn.sub.0.2Cu.sub.0.20Co.sub.0.06Fe.sub.1.96SO.sub.4 over the frequency range 100-200 MHz. They show advantageous performance with dielectric losses tan(δ.sub.ε) <0.006 and a dielectric constant ε′≈13-14.

[0129] These results support the scope of the invention in its generality. In particular, the examples support that the Ni/Zn ratio and the cobalt content defined according to the invention make it possible to adapt the targeted behaviour. Starting with one of the compositions of the examples according to the invention and varying one parameter in one direction and the other in the opposite direction, this achieves a similar result in terms of magnetic permeability μ′, dielectric permittivity ε′ and magneto-dielectric losses tan(δ.sub.μ)+tan(δ.sub.ε). Thus, there are a large number of possible compositional variants with similar performance to that shown in the examples.