Coherent superheterodyne electron paramagnetic resonance spectrometer

FIELD: radio engineering, communication.

SUBSTANCE: invention relates to applied physics and can be used in making electron paramagnetic resonance (EPR) spectrometers. The spectrometer comprises signal 1 and heterodyne 2 microwave generators, a measuring attenuator 3, reference 4 and signal 5 channel mixers, a circulator 6 with a measuring resonator 7, reference 8 and signal 9 channel intermediate-frequency amplifiers, phase-frequency discriminators 10 and 11, frequency dividers 12 and 13, synchronous detectors 14 and 15, phase changers 16 and 17, a resonance frequency adjustment element of the measuring resonator 18, microwave power dividers 19 and 20, an operating mode three-way switch 12, a reference frequency synthesis device 22, a reference generator 23.

EFFECT: simple device, smaller dimensions thereof, low power consumption and phase noise of the microwave generator.

1 dwg

 

The invention relates to the technical physics and can be used in the manufacture of spectrometers electron paramagnetic resonance (EPR).

Famous EPR spectrometer (Guy Rogeret al. Use of a digital PLL in an ESR heterodyne spectrometer // T. Phys R: Sci Instrum, 1981, v.14, p.335-338.), containing heterodyne signal and the microwave generators, mixers reference and signal channels, the circulator with a measuring resonator, measuring the attenuator. Microwave phase shifter, a frequency discriminator based on the reference high-q resonator, the modulation system-locked loop frequency signal of the microwave generator, the intermediate frequency amplifiers (HRC) reference and signal channels, synchronous detector intermediate frequency, the system phase-locked loop (PLL) heterodyne oscillator high-stability reference source of intermediate frequency and the mode switch, and the output of the heterodyne oscillator is connected to heterodyne the input of the reference channel mixer and the phase shifter, the output of which is connected to the heterodyne input of the mixer signal channel, the output of the signal generator is connected to the signal input of the mixer reference signal, the input of a frequency discriminator and the input of the measuring attenuator, first arm of the circulator is connected to the measuring output of the attenuator, the second with measuring�individual resonator, and the third signal input of the signal channel mixer, the mixer output signal channel is connected to the input of the HRC channel signal, and its output to the signal input of the synchronous detector intermediate frequency, the mixer output of the reference channel is connected to the input of the system phase-locked heterodyne microwave generator and to the input of the HRC reference channel, the output of the Commissioner, the reference channel is connected to the reference input of synchronous detector intermediate frequency, the modulation input of the auto-tuning system frequency through the function switch connects either the output of the frequency discriminator or the output of the synchronous detector intermediate frequency, and its output is connected to the control electrode of the signal generator, the output of the system phase-locked heterodyne microwave generator is connected to its control electrode.

However, this spectrometer is hard to configure, due to the need for selecting the desired phase relation by an adjustable microwave phase shifter for each installation of the measuring attenuator, has a lack of stability associated with the independence of the potentially unstable configuration of the microwave phase shifter and the measurement of the attenuator; insufficient resolution, which involves the use of a modulation locked loop system �of astate, reducing the spectral purity of the microwave signal, but is required when non-permanent phase relationships, in the apparatus for different settings of the measuring attenuator

Closest to the invention is an EPR spectrometer (Patent SU # 1739751, IPC6G01N 24/10, publ. 10.10.1995), containing the signal and heterodyne microwave generators, measuring resonator, mixers reference and signal channels, the circulator, the measuring resonator, the HRC reference and signal channels, two phase discriminator, a highly stable reference oscillator, two synchronous detectors, two of the phase shifter, the third mixer, the third Commissioner, the harmonics generator, the mode switch and the adjustment element measuring the resonant frequency of the resonator, and the Commissioner, the reference channel is made as a normalizing amplifier-shaper, the shifters have a fixed phase shift, measuring the output of the attenuator is connected to the input of the first power divider microwave, one of the outputs of which is connected to the first arm of the circulator, and the second signal input of the reference channel mixer, the output of the heterodyne oscillator is connected to the input of the second power divider, one output of which is connected to the heterodyne input of the mixer reference channel and the second with the heterodyne input of the mixer channel signal, the second shoulder circus�the fan motors are connected with the measuring resonator, equipped with element of restructuring its resonant frequency, the third arm of the circulator is connected to the input of the mixer channel signal, and its output - with the input of the HRC signal channel, the output of which is connected to the signal inputs of the first and second synchronous detectors, the output of the first shifter connected to the reference input of one of the synchronous detectors and the second input of the phase shifter, the output of which is connected to the reference input of the second synchronous detector, the output of the second phase discriminator is connected to the control electrode of the heterodyne oscillator, and a mode switch is made three-position, in the first and second position providing a connection Manager frequency electrode signal generator with the output of the first phase discriminator, and the third with the output of the first synchronous detector, the second position for connecting the output of the first synchronous detector element with adjustment of the resonance frequency of measurement resonator, and the Commissioner, the reference channel is made in the form of the normalizing amplifier shaper voltage, wherein the first and second phase shifters of the inverter is made with a fixed phase shift and the phase shift of the second is ±π/2.

The disadvantage of this device lies in the fact that in the stabilization mode �of astate signal generator external (absolute) standard loop PLL operates using the signal obtained by mixing the stabilized signal generator with one of the signals of a grid of frequencies obtained by multiplying the frequency of a highly stable reference oscillator, the subsequent selection and amplification of differential signals with a special selective amplifier. This decision has a schematic and structural complexity, has considerable dimensions, consumes significant power and is a source of additional phase noise of the stabilized oscillator.

Another disadvantage of this device is the use for meshing the reference frequency and the reference signal in the phase discriminators and phase-sensitive (synchronous) detector signal of fixed frequency high-stability reference oscillator, which complicates the construction of the loop PLL with integrated microelectronic solutions.

The object of the invention is to simplify the device, reducing its size, power consumption and cost, reducing the phase noise of the microwave generator, the implementation of the required functionalities on a typical, commercially available microelectronic components.

The task is achieved due to the fact that coherent superheterodyne spectrometer electron paramagnetic resonance, including signal and heterodyne microwave generators, �VA power divider microwave, mixers reference and signal channels, the circulator with a measuring resonator element and adjustment of the resonant frequency of the measurement resonator, measuring attenuator, amplifiers intermediate frequency (HRC) reference and signal channels, two phase-frequency discriminator with filters on outputs, two synchronous detectors, two Phaser inverter, reference oscillator and the switch works, and measuring the output of the attenuator is connected to the input of the first divider of microwave power, one of the outputs of which is connected to the first arm of the circulator, and the second signal input of the reference channel mixer, the output of the heterodyne oscillator is connected to the input of the second power divider, one of the outputs of which is connected to the heterodyne input of the mixer reference channel and the second with the heterodyne input of the mixer signal channel, the second arm of the circulator is connected with the measuring resonator element is provided with adjustment of its resonant frequency, the third arm of the circulator is connected to the input of the mixer channel signal, and its output - with the input of the HRC signal channel, the output of which is connected to the signal inputs of the first and second synchronous detectors, the output of the first shifter connected to the reference input of one of the synchronous detectors and the second input of the phase shifter, the output� of which is connected to the reference input of the second synchronous detector, the output of the second phase discriminator is connected to the control electrode of the heterodyne oscillator, and a mode switch is performed three position, the first and second position providing a connection Manager frequency electrode signal generator with the output of the first phase discriminator, and the third with the output of the first synchronous detector, the second position for connecting the output of the first synchronous detector element with adjustment of the resonance frequency of measurement resonator, and the Commissioner, the reference channel is made in the form of the normalizing amplifier shaper voltage, wherein the first and second phase shifters of the inverter is made with a fixed phase shift and the phase shift of the second is ±π/2, further comprises two frequency divider, the device of the synthesis of the reference frequency, and the signal generator is equipped with an additional output, and the output of the reference oscillator is connected to the input device of the synthesis of the reference frequency, one of the outputs of which is connected to the reference input of the first phase discriminator, the second reference input of the second phase-frequency discriminator, and the third with the input of the first phase shifter, and the auxiliary output of the signal generator via a first frequency divider connected to the signal input of the first�th phase-frequency discriminator, the input of the second frequency divider connected to the output of the HRC reference channel and its output to the reference input of the second phase-frequency discriminator.

The drawing shows a block diagram of the coherent superheterodyne EPR spectrometer.

The spectrometer contains a signal 1 and heterodyne 2 microwave generators, measuring the attenuator 3, the mixer 4 taps and mixer 5 signal channels, the circulator 6 to the measuring resonator 7, 8 support HRC and the HRC 9 of signal channels, the phase discriminators 10 and 11, the frequency dividers 12 and 13, the synchronous detectors 14 and 15, phase shifters 16 and 17, the adjustment element measuring the resonant frequency of the resonator 18, dividers, microwave power 19 and 20, three-way switch 21 of the operating modes, the device of the synthesis of the reference frequency 22, reference oscillator 23.

The device operates as follows.

The signal from the main output signal of the microwave generator 1, an electric oscillation is described by the function cos(ωmt), through the measuring attenuator 3, which gives the phase shift α is input to the power divider 19. Of the power branches off at the signal inputs of the mixer 4 of the reference channel, reaching it with additional phase shift φ1. On the reference input of the mixer through a power divider 20 is supplied to the signal heterodyne microwave generator 2, having the form cos(ωLt+λ+β1), g�e λ - phase fluctuations at the output of the heterodyne oscillator, a β1 - phase shift of the power divider and connectors. The difference signal from the output of the mixer 4 is amplified HRC 8 control channel, characterized by a wide dynamic range and low dependence of the delay (phase shift) on the magnitude of the input signal and is subjected to frequency division by N2 times the corresponding frequency divider 12. The signal output from the frequency divider 12 is supplied to the signal input of the phase discriminator 10 in the formcos((ωL-ωM)N2t+λ+β1-α-ϕ1N2+δ),

where δ describes the phase foray on the path from the output of the mixer 4 to the input 10.

Loop PLL intermediate frequency is closed by the output signal of the phase discriminator 10 through a filter (not shown for simplicity) to the input of the heterodyne oscillator 2, managing its frequency. On the reference input of the phase discriminator 10 is fed a highly stable signal

cos(ΩN2 t+γ),

where Ω is the intermediate frequency (if), and

γ is an arbitrary initial phase, with one of the outputs of the synthesis of the reference frequency 22.

When capturing loop PLL, the condition of equality with the input frequencies

(ωL+ωM)=Ω(1)

and phases

λ+β1-α-ϕ1N2+δ=γ.(2)

The main part of the microwave power signal generator 1 via the power divider 19 is supplied to the first shoulder of the microwave circulator 6 and further to the measuring resonator 7 is connected to the shoulder 2 of the circulator. Reflected from the resonator 7, the signal returns to the shoulder 2 of the circulator and then goes to his shoulder 3 connected to the signal input of the mixer 5 channel signal. With�drove this input is described by a function

G ' cos(ωmt+α+φ2)+G sin(ωmt+α+φ2),

where G' is the real part of the complex reflection coefficient of the resonator 7, depending on the absorption signal of the EPR,

G” is the imaginary part, depending on the signal variance of the EPR and the detuning of the resonator relative to the frequency of the incident wave,

φ2 is the phase shift of the microwave wave from the input of the power divider 19 to the input of the mixer 5.

The output of the mixer 5 the difference signal is input to the HRC 9 channel signal and a further signal inputs of the synchronous detectors 14 and 15 in the form

G'cos((ωL-ωM)t+λ+β2-α-ϕ2+η)--G''sin((ωL-ωM)t+λ+β2-α-ϕ2+η),(3)

where η indicates the phase shift from the output of the mixer 5 to the inputs of the synchronous� detectors 14 and 15.

In terms of the capture loop PLL intermediate frequency function of (1) and (2) for frequencies and phases, which leads to the fact that the signal (3) takes the form

G'cos(Ωt+(γ-δ)N2-β1+ϕ1+β2-ϕ2+η)--G''sin(Ωt+(γ-δ)N2-β1+ϕ1+β2-ϕ2+η),(4)

Thus, the received signal at intermediate frequency contains About two quadrature components, one of which is proportional to G', i.e., the absorption signal ESR and the second G”, i.e. the signal dispersion and detuning of the measuring resonator.

A highly stable reference signal cos(Ωt)c one of the outputs of the synthesis of the reference frequency 22 is input to the phase shifter 17, which gives the phase foray θ. The signal output from futurama�'el 17 cos(Ωt+θ) is supplied to the reference input of the mixer 14 and the second shifter 16, rotating the phase by ±π/2. Thus, taking, for definiteness, a shift of-π/2, we get the output of the phase shifter 16 is connected to the reference input of the mixer 15, sin(Ωt+θ). As a result of mixing and highlight the difference frequency will receive the output 15

G'sin((γ-δ)N2-β1+ϕ1+β2-ϕ2+η-θ)--G''cos((γ-δ)N2-β1+ϕ1+β2-ϕ2+η-θ),(5)

and outlet 14

G'cos((γ-δ)N2-β1+ϕ1+β2-ϕ2+η-θ)--G''sin ((γ-δ)N2-β1+ϕ1+β2-ϕ2+η-θ),(6)

Phase angle, which is the trigonometric functions (5) and (6), do not contain significantly variable α that depend on the installation of measuring attenuator 3, and is determined only by constant phase shifts in the various circuits of the device. Thus, by setting the phase shift θ of the phase shifter 17 so that the phase angle (γ-δ)N2-β1+φ1+β2-φ2+θ was equal to π/2 or 3π/2, we get the output 15 net absorption signal, and the output 14 signal proportional to the dispersion and measuring the detuning of the resonator regardless of the frequency of the measuring oscillator 1, the relative detuning of the resonance frequency of measurement resonator 7 and the power level. Reference signal for operation of the device of the synthesis of the reference frequency 22 is the output signal of highly stable reference oscillator 23 to a comfortable working 22 frequency.

The machine has three mode frequency stabilization of the measuring generator 1 and resonance frequency of measurement resonator�of 7 nator. For absolute stabilization (stabilization of highly stable standard frequency signal generator uses an auxiliary frequency output of the signal generator 1. In his absence he can easily be created by incorporating the directional coupler on the main (only) the output of the generator. The microwave signal from the auxiliary output is subjected to division by the frequency divider 13 in N1 times to a frequency convenient for comparison to the phase discriminator 11, and is supplied at its signal input in the formcos(ωmN1t). On the reference input of the discriminator is fed a highly stable signal from one of the outputs of the synthesis of the reference frequency 22 of the formcos(ωm0N1t)where ωM0- rated frequency of the measuring oscillator. In position "1" switch kind of works 21 loop PLL the frequency of the signal generator is energised by the signal testing with gate 11 through an appropriate filter (for simplicity not shown) to the electrode that controls the frequency of 1. Hour�OTA signal generator 1 is stabilized at the value of ω M0that allows to tune the resonance frequency of measurement resonator 7 to coincide with ωM0. In position "2" switch kind of works 21 the output signal of synchronous detector 14 in the corresponding phase is supplied to the adjustment element resonant frequency 18 of the measuring resonator 7 to automatically adjust its resonant frequency under stable signal generator 1. Finally, in the third position signal 21 output from the synchronous detector 14 is used for adjustment of oscillation frequency 1 under the instantaneous resonance frequency of measurement resonator 7, for what it is in that phase is sent to a control frequency of the electrode 1.

Thus, the operation of the spectrometer, including the allocation of the net signals of absorption and dispersion, is achieved through using standard, commercially available hardware components (frequency dividers, frequency synthesizers with phase discriminators) that provides a reduction in size, power consumption and price of the device, improves manufacturability and reliability, reduces phase noise.

Coherent superheterodyne spectrometer electron paramagnetic resonance, including signal and heterodyne microwave generators, two power divider microwave, mixers support and signalnamechanged, a circulator with a measuring resonator element and adjustment of the resonant frequency of the measurement resonator, measuring attenuator, amplifiers intermediate frequency (HRC) reference and signal channels, two phase-frequency discriminator with filters on outputs, two synchronous detectors, two Phaser inverter, reference oscillator and the switch works, and measuring the output of the attenuator is connected to the input of the first divider of microwave power, one of the outputs of which is connected to the first arm of the circulator, and the second signal input of the reference channel mixer, the output of the heterodyne oscillator is connected to the input of the second power divider, one of the outputs of which is connected to the heterodyne input of the mixer reference channel and the second with the heterodyne input of the mixer signal channel, the second arm of the circulator is connected with the measuring resonator element is provided with adjustment of its resonant frequency, the third arm of the circulator is connected to the input of the mixer channel signal, and its output - with the input of the HRC signal channel, the output of which is connected to the signal inputs of the first and second synchronous detectors, the output of the first shifter connected to the reference input of one of the synchronous detectors and the second input of the phase shifter, the output of which is connected to the reference input of the second�about synchronous detector, the output of the second phase discriminator is connected to the control electrode of the heterodyne oscillator, and a mode switch is performed three position, the first and second position providing a connection Manager frequency electrode signal generator with the output of the first phase discriminator, and the third with the output of the first synchronous detector, the second position for connecting the output of the first synchronous detector element with adjustment of the resonance frequency of measurement resonator, and the Commissioner, the reference channel is made in the form of the normalizing amplifier shaper voltage, wherein the first and second phase shifters of the inverter is made with a fixed phase shift and the phase shift of the second is ±π/2, characterized in that it further comprises two frequency divider, the device of the synthesis of the reference frequency, and the signal generator is equipped with an additional output, and the output of the reference oscillator is connected to the input device of the synthesis of the reference frequency, one of the outputs of which is connected to the reference input of the first phase discriminator, the second reference input of the second phase-frequency discriminator, and the third with the input of the first phase shifter, and the auxiliary output of the signal generator via the first frequency divider is connected � signal input of the first phase discriminator, the input of the second frequency divider connected to the output of the HRC reference channel and its output with the reference input of the second phase-frequency discriminator.



 

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