JP2847747B2 - Magnetostatic wave delay line type oscillator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to, for example, a VCO (voltage-controlled oscillato).
The present invention relates to a magnetostatic wave delay line oscillator (Magnetostatic Wave Delay Line Oscillator) used for a voltage controlled oscillator (r) and the like, and relates to an oscillator in which SSB phase noise is optimized.

<Related Art> First, a delay element of a magnetostatic wave delay type oscillator will be briefly described. When a magnetic transducer and two transducers made of metal conductors are placed close to each other in a uniform magnetic field, and a high-frequency current is applied to one of the two transducers, the spin in the magnetic substance nearby fluctuates. The fluctuation propagates as a magnetostatic wave, and a high-frequency induced current due to the fluctuation of the spin flows through the other transducer. Since the propagation speed of the spin fluctuation changes according to the strength of the magnetic field, the element has a variable delay time.

FIG. 4 is a block diagram showing a magnetostatic wave delay linear oscillator using the magnetostatic wave delay element. In the figure, reference numeral 1 denotes a magnetostatic wave delay element, which is formed by forming transducers 5a and 5b on a substrate made of an insulating material at a predetermined interval 1 and approaching or in contact with the transducer to cause GGG.
(Gadolinium-gallium-garnet) It is composed of a YIG thin film formed on a substrate. 2 is an amplifier, 3 is a coupler, and 4 is a spectrum analyzer. The length of the wavelength of the magnetostatic wave to be transmitted and received is determined by the distance a between the transducers.
Determined by

Magnetic field H _o by the magnetic field applying means (not shown) in the delay element
Is applied, a frequency signal flowing through the loop is taken into the spectrum analyzer 4 via the coupler 3, and the oscillation frequency characteristic is measured.

In the figure, the high-frequency current flowing through the input transducer 5a causes the electron spin in the magnetic material to fluctuate and become a magnetostatic wave, which propagates to the output transducer 5b. This output is amplified by the amplifier 2 and output via the coupler 3. The delay element → amplifier → coupler → delay element is connected by microwave cables 5a, 5b, 5c.

By the way, when designing such a delay element, SSB
It is necessary to determine an optimal group delay time that minimizes phase noise. The SSB phase noise will be briefly described.

FIG. 5 shows a spectrum of a frequency oscillated when a constant magnetic field is applied to the oscillator having the above configuration. This According to FIG f _o center frequency of the power peak of (Ps), and the frequency of the back and forth is gently power is reduced. The ratio of the power density of a frequency away from the total power and peak of the entire signal (practically in the power ... Figure frequencies before and after the power of the peak frequency away fm from the power Ps and f _o of the frequency f _o Frequency power ratio Pss
b / Ps) is called SSB phase noise L (fm), and the smaller the ratio, the better.

<Problem to be Solved by the Invention> In the magnetostatic wave delay type oscillator having the above-described configuration, the optimum group delay time τ _ga for minimizing the SSB phase noise has conventionally used a value calculated by the following equation.

In _{τ ga [μsec] = 8.7 [} dB] / {76.4 [dB / (μsec · O e)] · ΔH [O e]} = 114 [nsec · O e] / ΔH [O e] ...... above equation, 8.7 [dB] is a value reported by W. Ishak et al., IEEE TRANSACTIONS MAGNET ICS VOL.MAG20, NO.
5 “TUNABLE MAGNETIC WAVE OSCILLATORS USING PURE AND
DOPED YIG FILMS ".

However, the value of τ _ga calculated by the above equation is calculated by ignoring the residual phase noise of the amplifier included in the oscillator. Therefore, the propagation length of the magnetostatic wave is determined by the value obtained by the above equation. However, there is a problem that an optimum SSB phase noise cannot be obtained.

The present invention has been made in view of the above-mentioned problems of the prior art, and determines an optimum group delay value in consideration of the residual phase noise of an amplifier, and based on the value, determines the minimum SSB phase noise so as to minimize the SSB phase noise. It is an object of the present invention to provide a magnetostatic wave delay line type oscillator whose dimensions are determined.

<Means for Solving the Problems> According to a configuration of the present invention for solving the above problems, a YIG thin film having a thickness t formed on a substrate and a YIG thin film formed on the YIG thin film at a constant distance 1 are provided. A magnetostatic wave delay line oscillator comprising an input / output transducer and an amplifier for amplifying a magnetostatic wave having a wavelength λ that is excited by a signal input to the input transducer and propagates to the output transducer. If the SSB phase noise due to the residual phase noise of the amplifier at the optimal group delay value (τ _gs ) at which the SSB phase noise to be minimized is greater than the SSB phase noise due to the YIG thin film, the optimal group delay of the magnetostatic wave The value is calculated by the following equation, and the values of l, t, λ are determined based on the calculation result, and the SSB phase noise of the output signal from the oscillator is minimized. Than it is.

Note that τ _gs = ｛(L (f) −Pn−F + Pin) / (76.4 × 1
0 ⁶ )｝ × (1 / ΔH) [sec] where L (f): amplifier residual phase noise [dBc / Hz] F: amplifier noise figure [dB] Pin: magnetostatic wave delay line input [dBm] ΔH; YIG magnetic resonance half width [O _e ] Pn; Thermal noise level [dBm / Hz] 76.4 × 10 ⁶ ; Proportional constant between τ _g (group delay time of magnetostatic wave) and delay line loss <Action> Optimal group When calculating the delay time, each dimension is determined so as to minimize the SSB phase noise by using a calculation formula that takes into account the influence of the residual phase noise of the amplifier in addition to the phase noise from YIG and the noise figure of the amplifier.

<Example> Hereinafter, the present invention will be described.

In the present invention, the optimum group delay value (τ _gs ) of the magnetostatic wave is calculated by the following formula, and based on the calculation result, (1) the interval l between the input and output transducers l (2) the thickness t (3) of the YIG thin film Determine any unknown value of the propagating wavelength λ.

τ _gs = ｛(L (f) −Pn−F + Pin) / (76.4 × 1
0 ⁶ )｝ × (1 / ΔH) [sec] where L (f): amplifier residual phase noise [dBc / Hz] F: amplifier noise figure [dB] Pin: magnetostatic wave delay line input [dBm] ΔH: YIG magnetic resonance half width [O _e ] Pn; thermal noise level (−177) 76.4 × 10 ⁶ ; proportional constant L of τ _g (group delay time of magnetostatic wave) and loss L [dB] of delay line [DB] = 76.4 · 10 ⁶ [dB / (O _e · s)] ΔH [O _e ] · τ _g [s] Here, the wavelength (λ) of the magnetostatic wave and the thickness (t) of the YIG are known. Let us consider the case where the interval l of the transducer is obtained. The type of the magnetostatic wave is a volume forward wave.

_{l = υ g · τ gs ......} υ g = dω / dκ tan (κt / α) = α α 2 = [{ω / (2π · γ)} 2 - (Hi) 2] / [Hi (4πM s + Hi ) − ｛Ω / (2π ·
γ)｝ ² ] where, υ _g ; group velocity of magnetostatic wave ω; angular frequency of magnetostatic wave κ; wave number of magnetostatic wave (2π / λ) α; dimensionless number t; YIG film thickness γ; rotation ratio (~2.8MHz / Oe) ω / 2π ; frequency magnetostatic wave Hi; YIG internal magnetic field 4 [pi] Ms; YIG saturation magnetization above t, λ, γ, Hi, in formula seek upsilon _g from a known number of 4PaiM _s The length l of the transducer is determined by the equation from the product of the obtained τ _gs .

For example, when the optimum group delay value (τ _gs ) for minimizing the SSB phase noise L (f _m ) at a position 10 kHz away from the center wavelength is calculated, the following is obtained.

 The conditions are as follows.

YIG magnetic resonance half width (ΔH); 1.0 O _e , amplifier noise figure (F); 4 [dB] magnetostatic wave delay line input (Pin); 10 [dBm] amplifier residual phase noise L (f); _{160 [dBc / Hz] τ gs} = {(- 160 + 177-4 + 10) / (76.4 × 10 6)} × (1 / 1.0) = 301 [nsec] YIG saturation magnetization of using the result; 1760O _e (YIG standard physical properties values) external magnetic field; 2460O _e as the propagation length lmm and Ramudamm, become table below as the determining a relationship Timyuemu.

In the conventional formula for calculating the optimum group delay time (see formula), τ _ga = 114 / 1.0 = 114 [nsec], so the value of lmm in the table is about 1/3.

Further, in the conventional example of calculation formula Figure 6 as shown in (a) tau _ga is the but Q value becomes SSB phase noise decreases significantly the value of tau _ga exceeds a predetermined value greater loss increases SSB Phase noise increases. Although Although this conventional formula are the contains the noise figure F as amplifier noise to affect the magnitude of the noise figure SSB phase noise (FIG. 6 b refer) tau value of _ga can SSB phase noise Is still the value for choosing the minimum. The minimum phase noise L (F _m ) considering the residual phase noise of the amplifier can be expressed by the following equation.

_{L (F m) = max [} Lω, L (f)] - 20log 1 (2πF m τ g) = max [{Lω-20log 1 o (2πF m τ g)}, {(f) -20log 1 o ( 2πF _m τ _g )｝]... In the equation, one item of max is YIG noise (more precisely, the contribution of phase noise due to mature noise), and two items are the residual phase noise of the amplifier. (Conventionally, only one item was considered) Here, Lω is given by Lω = −177 + F−Pin + 76.4 · 10 ⁶ ΔH · τ _g .

The relationship between the phase noise of each term in the equation and the optimum group delay time can be expressed as shown in FIG. In FIG. 1, the straight line a is due to the residual phase noise of the amplifier, and the curve b is due to the YIG noise. In the figure, point P ₀ is YIG
This is the point where the phase noise due to noise is minimized.
If τ _ga is selected here, the amplifier residual phase noise P ₁ at a higher level becomes SSB phase noise. P ₂ points it is understood that the amplifiers of the residual phase noise is the point determined by the equation considering the SSB phase noise from the point of P ₁ of the present invention can be reduced.
Incidentally, you can apply a formula of the invention is only when the intersection of the straight line and b of the curve b is on the right side than P ₀ point.

FIG. 2 shows the case where the residual phase noise of the amplifier and the input to the magnetostatic wave delay line become small and τ _ga > τ _gs (that is, the intersection of the line a and the line B comes to the left of the point P ₀ ). ) YIG
It shows the relationship between noise and amplifier noise. According to the figure, the point of τ _ga calculated only for YIG noise is obtained from the value of τ _{gs which} is the intersection point P _{4 of} the phase noise caused by YIG noise and the residual phase noise of the amplifier, and the minimum SSB phase noise can be obtained. Value. In such a case, the minimum delay time is calculated using a conventional equation. Note that which of τ _ga and τ _gs is larger can be determined by the following equation.

τ _ga = 8.69 ｛1 / (76.4 · 10 ⁶ )｝ τ _gs = ｛L (f) + 177−F + Pin｝ ｛1 / (76.4 · 1
0 ^6)} The arrangement of the input and output transducers formed on the substrate, for example 3 (a), be those (b) in as shown (with a longer propagation length l without increasing the shape of the substrate) May be.

<Effect of the Invention> As described above, according to the present invention, any one of the unknown values of l, t, and λ is designed by using the optimal group delay time including the residual phase noise of the amplifier. The magnetostatic wave delay type oscillator with the minimum SSB phase noise can be realized.

[Brief description of the drawings]

1 and 2 show the relationship between the noise caused by the YIG thin film, the SSB phase noise caused by the residual phase noise of the amplifier, and the group delay time, and FIG. 3 shows the shapes of the substrate and the YIG thin film changed. FIG. 4 is a diagram showing a state, FIG. 4 is a configuration diagram showing a general magnetostatic wave delay linear oscillator, FIG. 5 is a diagram showing a relationship between frequency and power for explaining SSB phase noise, and FIGS.
(B) is a diagram showing a relationship between SSB phase noise and τ _ga .
1 ... magnetostatic wave delay element, 2 ... amplifier, 3 ... coupler, 5a ...
… Input transducer, 5b …… output transducer.

──────────────────────────────────────────────────続 き Continuation of front page (56) References 1986 IEICE General Conference, Article No. 814 Ishak, “TUNABLE MAGNETIC WAVE OSCI LLATORS USING PURE AND DOPED YIG FIL MS”, IEEE TRANSACTION NS MAGNETICS VOL. M AG20, NO. 5, (58) Field surveyed (Int. Cl. ⁶ , DB name) H03B 5/18 H03H 9/68, 9/25 H01P 9/00

Claims (1)

(57) [Claims] A YIG thin film having a thickness of t formed on a substrate, an input / output transducer formed on the YIG thin film at a predetermined distance l, and a signal inputted to the input transducer being excited by the signal; In a magnetostatic wave delay linear oscillator including an amplifier for amplifying a magnetostatic wave having a wavelength of λ propagating to the output transducer, an optimal group delay value (τ _gs ) at which SSB phase noise caused by the YIG thin film is minimized. If the SSB phase noise caused by the residual phase noise of the amplifier is larger than the SSB phase noise caused by the YIG thin film, the optimum group delay value of the magnetostatic wave is calculated by the following equation, and based on the calculation result, , t, λ are determined, and the SSB phase noise of the output signal from the oscillator is minimized. Note τ _gs = {(L (f) −Pn−F + Pin) / (76.4 × 10 ⁶ )} × (1 / ΔH) [sec] where L (f); residual phase noise of amplifier [dBc / Hz] F; noise figure of the amplifier [dB] Pin; magnetostatic wave delay line input [dBm] ΔH; YIG magnetic resonance half-width [O _e] Pn; thermal noise level [dBm / Hz] 76.4 × 10 6; τ g ( magnetostatic wave Group delay time… variable) and delay line loss proportional constant