CN104634540A - Testing system and testing method for front end of heterodyne terahertz quasi-optical receiver - Google Patents

Abstract

The invention relates to the technical field of terahertz detection and testing and relates to a testing system and a testing method for testing a noise temperature of the front end of a heterodyne terahertz quasi-optical receiver. The system comprises a high-temperature blackbody radiation source, a frequency doubling link, a microwave signal source, a beam splitter, a terahertz quasi-optical frequency mixer, a BLAS (Basic Linear Algebra Subprogram) bias, a first-stage low noise amplifier, a second-stage low noise amplifier, a band-pass filter and a power meter. According to the testing system and the testing method, the high-temperature blackbody source is used as a terahertz noise signal source, so that a temperature variation range of the terahertz noise signal source is enlarged and a noise temperature testing range of the testing system is effectively enlarged; a terahertz quasi-optical lens is used as a beam bunching device of the terahertz frequency mixer, so that detection sensitivity of a front end system of the heterodyne terahertz quasi-optical receiver is improved and the problems of weak terahertz noise signal and difficulty in detection on the terahertz noise signal are solved.

Description

The test macro of the quasi-optical receiver front end of a kind of heterodyne system Terahertz and method of testing

Technical field

The present invention relates to terahertz detection and technical field of measurement and test, relate to test macro and the method for testing of the noise temperature of the quasi-optical receiver front end of a kind of heterodyne system Terahertz.

Background technology

Terahertz refers to that frequency is 0.1-10THz (1THz=10 ¹²hz) electromagnetic wave of scope, corresponding wavelength scope is 3mm-30 μm, between millimeter wave and infrared waves.THz wave is difficult to produce and detection by traditional electronics and optical means, and therefore, terahertz wave band is considered to the last blank of electromagnetic wave spectrum, is called Terahertz space.Along with the development of Terahertz Technology, Terahertz Technology has been applied to radio astronomy, earth atmosphere observation, Terahertz logical letter ﹑ short distance high sensitivity thunder reaches is that system ﹑ medical science and biology study the fields such as picture ﹑ earth environment monitoring and fast wireless network, so the research of THz imaging technology is a very important research direction at present.The highly sensitive terahertz detector of current research is an important component part of research terahertz imaging system.The development relative maturity of infrared eye and millimeter wave receiver, its radiation detection theory is respectively based on Wien's radiation law and Ruili Jones's law.THz wave has had both advantage concurrently between infrared and millimeter wave, and the noise temperature system testing for the quasi-optical receiver front end of Terahertz is also in developing stage.So research is applicable to the theory of testing of the noise temperature of the quasi-optical receiver front end of Terahertz and method seems particularly important.

The measuring method of noise temperature mainly contains the direct method of measurement, gain measurement method, twice power method and Y factor method.Because the direct method of measurement and gain measurement method need the gain knowing frequency mixer in advance, and twice power method is difficult to the power of Measurement accuracy output signal when weak output signal, all effectively can not apply and test with the noise temperature of Terahertz frequency range.

Summary of the invention

The object of the invention is to overcome the deficiencies in the prior art, there is provided a kind of test macro and the method for testing that can measure reliably and accurately the noise temperature of the quasi-optical receiver front end of heterodyne system Terahertz, this system can reasonably utilize cold and hot load method to measure the noise temperature of the quasi-optical receiver front end of heterodyne system Terahertz.

The object of the invention is to be achieved through the following technical solutions.

The noise temperature test macro of the quasi-optical receiver front end of a kind of heterodyne system Terahertz of the present invention, this system comprises that high temperature blackbody radiation source, frequency multiplication link, microwave signal source, beam splitter, Terahertz quasi-optical frequency mixer, BLAS are biased, first order low noise amplifier, second level low noise amplifier, bandpass filter and power meter.

High temperature blackbody radiation emission Terahertz noise signal, Terahertz noise signal enters Terahertz quasi-optical frequency mixer through the part of beam splitter;

Microwave signal source launched microwave signal, microwave signal forms local oscillation signal through frequency multiplication link frequency multiplication after Terahertz frequency range, and local oscillation signal enters Terahertz quasi-optical frequency mixer through the part of beam splitter reflection;

The Terahertz noise signal and the local oscillation signal that enter into Terahertz frequency mixer carry out mixing, intermediate-freuqncy signal is obtained after mixing, the intermediate-freuqncy signal obtained, more successively through first order low noise amplifier, second level noise amplifier, bandpass filter and power meter, realizes the overall process that the quasi-optical receiver front end noise temperature of heterodyne system Terahertz is measured.

The method of testing of the noise temperature of the quasi-optical receiver front end of heterodyne system Terahertz, step is:

This method of testing improves traditional millimere-wave band the is similar to Planck's law of radiation theory of testing with Rayleigh-Jones's law, and obtain the more accurate noise temperature theory of testing by carrying out Taylor expansion to Planck law and choosing higher order term, particular content is as follows:

The brightness B of Planck law _fformula:

$B_f=\frac{2h{f}^3}{c^2}\left(\frac{1}{e^{\mathrm{hf}/\mathrm{kT}}-1}\right)---\left(1\right)$

Wherein, c is the light velocity, and h is Planck's constant, and k is Boltzmann constant, and f is frequency, and T is radiation temperature.

Order by e ^afcarry out Taylor expansion:

$e^{\mathrm{Af}}=1+\mathrm{Af}+\frac{1}{2}{A}^2{f}^2+\frac{1}{6}{A}^3{f}^3......---\left(2\right)$

The radiance B ' of the improvement that the first three items of getting expansion item obtains _fformula be:

$B_f^{\′}=\frac{2\mathrm{kT}}{{\mathrm{\λ}}^2}\left(\frac{2\mathrm{kT}}{2\mathrm{kT}+\mathrm{hf}}\right)---\left(3\right)$

Wherein, λ is wavelength.

According to Ruili Jones's law, an antenna is placed in the blackbody radiation environment that a temperature is T, and the noise power P that calculating antenna receives is:

$P=\frac{1}{2}{A}_r{\∫}_f^{f+\mathrm{\Δf}}\underset{4\mathrm{\π}}{\∫\∫}\frac{2\mathrm{kT}}{{\mathrm{\λ}}^2}{F}_n(\mathrm{\θ},\mathrm{\φ})\mathrm{d\Ωdf}---\left(4\right)$

If the Power Limitation detected is in an arrowband Δ f, then the radiance of black matrix approximate constant in Δ f.

By aerial radiation solid angle Ω _pfor:

$\underset{4\mathrm{\π}}{\∫\∫}{F}_n(\mathrm{\θ},\mathrm{\φ})\mathrm{d\Ω}={\mathrm{\Ω}}_p---\left(5\right)$

${\mathrm{\Ω}}_p=\frac{{\mathrm{\λ}}^2}{A_r}---\left(6\right)$

Wherein F _nthe normalization antenna pattern that (θ, φ) is antenna, n represents normalization, and θ represents the elevation angle, and φ represents position angle, A _rfor the effective radiating area of antenna.

Can draw according to formula (4)-(6):

P＝kTΔf (7)

At the power density P that millimeter wave band Ruili Jones's law calculates ^r-J:

P ^R-J＝k·T (8)

In Terahertz frequency range by the power density P ' obtained of correction formula be:

$P^{\′}=\mathrm{kT}\left(\frac{2\mathrm{kT}}{2\mathrm{kT}+\mathrm{hf}}\right)\≡{\mathrm{kT}}^{\′}---\left(9\right)$

In conjunction with to the definition of noise temperature namely: noise temperature is that the radiation power of single frequency obtains the define method to the noise temperature T ' improved with the ratio of Boltzmann constant and to the define method of noise power:

$T^{\′}=T\left(\frac{2\mathrm{kT}}{2\mathrm{kT}+\mathrm{hf}}\right)---\left(10\right)$

Obtain the corresponding noise temperature T of this test macro _rcomputing formula:

$T_R=\frac{T_{\mathrm{hot}}^{\′}-{\mathrm{YT}}_{\mathrm{cold}}^{\′}}{Y-1}---\left(11\right)$

Wherein, T ' _hotwith T ' _coldfor the high temperature after improvement and the cold and hot load temperature under low temperature, Y is the Y factor value recorded.

The method of testing of the noise temperature of the quasi-optical receiver front end of heterodyne system Terahertz, below main testing procedure:

(1) key instrument of test is opened, the main devices of debugging test, the required function element in calibration, debugging and mounting test system and testing tool.

(2) by microwave signal source launch local oscillation signal through frequency multiplier frequency multiplication to Terahertz frequency range, enter Terahertz quasi-optical frequency mixer through beam splitter.

(3) the Terahertz noise signal produced under different radiation temperature by high temperature blackbody radiation source enters Terahertz quasi-optical frequency mixer through beam splitter, and two paths of signals carries out mixing and obtains intermediate-freuqncy signal in Terahertz quasi-optical frequency mixer.

(4) intermediate-freuqncy signal enters Computer display test result through low noise amplifier, bandpass filter, power meter.

(5) according to the method for Y factor, utilize above derivation formula, the noise temperature of the quasi-optical receiver front end of Terahertz can be calculated.

Beneficial effect

The present invention adopts two-stage low noise amplifier, increases the enlargement factor of intermediate-freuqncy signal, the entire gain of effective lifting force test macro, and the intermediate-freuqncy signal of solution is faint, easily by problem that noise floods; The present invention adopts high temperature blackbody source as Terahertz noise signal source, adds the range of temperature of Terahertz noise signal source, effectively expands the test specification of the noise temperature of test macro; The present invention adopts the quasi-optical lens of Terahertz as the bunching system of Terahertz frequency mixer, improves the detection sensitivity of heterodyne system Terahertz receiver front end system, efficiently solves Terahertz noise signal faint, is difficult to the problem detected.

Accompanying drawing explanation

Fig. 1 is the composition schematic diagram of system of the present invention.

Embodiment

In order to better show test macro of the present invention and method of testing, describe the present invention below in conjunction with the drawings and specific embodiments.

Embodiment

As shown in Figure 1, a noise temperature test macro for the quasi-optical receiver front end of heterodyne system Terahertz, this system comprises that high temperature blackbody radiation source, frequency multiplier, microwave signal source, beam splitter, Terahertz quasi-optical frequency mixer, BLAS are biased, first order low noise amplifier, second level low noise amplifier, bandpass filter and power meter.

High temperature blackbody radiation emission Terahertz noise signal, Terahertz noise signal enters Terahertz quasi-optical frequency mixer through the part of beam splitter;

Microwave signal source launched microwave signal, microwave signal forms local oscillation signal through frequency multiplication link frequency multiplication after Terahertz frequency range, and local oscillation signal enters Terahertz quasi-optical frequency mixer through the part of beam splitter reflection;

The Terahertz noise signal and the local oscillation signal that enter into Terahertz frequency mixer carry out mixing, intermediate-freuqncy signal is obtained after mixing, the intermediate-freuqncy signal obtained, more successively through first order low noise amplifier, second level noise amplifier, bandpass filter and power meter, realizes the overall process that the quasi-optical receiver front end noise temperature of heterodyne system Terahertz is measured.

The method of testing of the noise temperature of the quasi-optical receiver front end of heterodyne system Terahertz, is characterized in that comprising:

This method of testing improves traditional millimere-wave band the is similar to Planck's law of radiation theory of testing with Rayleigh-Jones's law, obtains the more accurate noise temperature theory of testing by carrying out Taylor expansion to Planck law and choosing higher order term.

The method of testing of the noise temperature of the quasi-optical receiver front end of heterodyne system Terahertz, main testing procedure:

(1) open the instrument of this test macro, carry out thermal pretreatment, the required function element in calibration, debugging and mounting test system and testing tool;

(2) by microwave signal source launch local oscillation signal through frequency multiplier frequency multiplication to Terahertz frequency range, enter Terahertz quasi-optical frequency mixer through beam splitter.

(3) the Terahertz noise signal produced under different radiation temperature by high temperature blackbody radiation source enters Terahertz quasi-optical frequency mixer through beam splitter, and two paths of signals carries out mixing and obtains intermediate-freuqncy signal in Terahertz quasi-optical frequency mixer.

(4) intermediate-freuqncy signal enters Computer display test result through low noise amplifier, bandpass filter, power meter.

(5) according to the method for Y factor, utilize above derivation formula, the noise temperature of the quasi-optical receiver front end of Terahertz can be calculated.

The computing method of described step (5) are:

The brightness B of Planck law _fformula:

$B_f=\frac{2h{f}^3}{c^2}\left(\frac{1}{e^{\mathrm{hf}/\mathrm{kT}}-1}\right)---\left(1\right)$

Wherein, c is the light velocity, and h is Planck's constant, and k is Boltzmann constant, and f is frequency, and T is radiation temperature.

Order by e ^afcarry out Taylor expansion:

$e^{\mathrm{Af}}=1+\mathrm{Af}+\frac{1}{2}{A}^2{f}^2+\frac{1}{6}{A}^3{f}^3......---\left(2\right)$

The radiance B ' of the improvement that the first three items of getting expansion item obtains _fformula be:

$B_f^{\′}=\frac{2\mathrm{kT}}{{\mathrm{\λ}}^2}\left(\frac{2\mathrm{kT}}{2\mathrm{kT}+\mathrm{hf}}\right)---\left(3\right)$

Wherein, λ is wavelength.

According to Ruili Jones's law, an antenna is placed in the blackbody radiation environment that a temperature is T, and the noise power P that calculating antenna receives is:

$P=\frac{1}{2}{A}_r{\∫}_f^{f+\mathrm{\Δf}}\underset{4\mathrm{\π}}{\∫\∫}\frac{2\mathrm{kT}}{{\mathrm{\λ}}^2}{F}_n(\mathrm{\θ},\mathrm{\φ})\mathrm{d\Ωdf}---\left(4\right)$

If the Power Limitation detected is in an arrowband Δ f, then the radiance of black matrix approximate constant in Δ f.

By aerial radiation solid angle Ω _pfor:

$\underset{4\mathrm{\π}}{\∫\∫}{F}_n(\mathrm{\θ},\mathrm{\φ})\mathrm{d\Ω}={\mathrm{\Ω}}_p---\left(5\right)$

${\mathrm{\Ω}}_p=\frac{{\mathrm{\λ}}^2}{A_r}---\left(6\right)$

Wherein F _nthe normalization antenna pattern that (θ, φ) is antenna, n represents normalization, and θ represents the elevation angle, and φ represents position angle, A _rfor the effective radiating area of antenna.

Can draw according to formula (4)-(6):

P＝kTΔf (7)

At the power density P that millimeter wave band Ruili Jones's law calculates ^r-J:

P ^R-J＝k·T (8)

In Terahertz frequency range by the power density P ' obtained of correction formula be:

$P^{\′}=\mathrm{kT}\left(\frac{2\mathrm{kT}}{2\mathrm{kT}+\mathrm{hf}}\right)\≡{\mathrm{kT}}^{\′}---\left(9\right)$

In conjunction with to the definition of noise temperature namely: noise temperature is that the radiation power of single frequency obtains the define method to the noise temperature T ' improved with the ratio of Boltzmann constant and to the define method of noise power:

$T^{\′}=T\left(\frac{2\mathrm{kT}}{2\mathrm{kT}+\mathrm{hf}}\right)---\left(10\right)$

Obtain the corresponding noise temperature T of this test macro _rcomputing formula:

$T_R=\frac{T_{\mathrm{hot}}^{\′}-{\mathrm{YT}}_{\mathrm{cold}}^{\′}}{Y-1}---\left(11\right)$

Wherein, T ' _hotwith T ' _coldfor the high temperature after improvement and the cold and hot load temperature under low temperature, Y is the Y factor value recorded.

The purport of test macro of the present invention and method of testing is: by improving the theory of testing of traditional millimeter wave receiver noise temperature of front end, and utilize high temperature blackbody radiation source, improves measurement range and the accuracy of test macro.

Step 1: according to test system structure block diagram test system building, open testing tool and preheating, the required device in debugging test.The temperature value of calibration high temperature blackbody radiation source, debugging Agilent signal source 8257D and power meter make it be operated in expecting state, and are installed on the securing means by Terahertz frequency mixer.What the local vibration source that this example utilizes adopted is the 24 frequency multiplication links that Beijing Institute of Technology designs; This tests Terahertz quasi-optical frequency mixer used based on Terahertz schottky diode; This tests beam splitter used be diameter is the smooth silicon chip of 10cm.

Step 2: Agilent signal source 8257D launches the 6 frequency multiplier frequencys multiplication of 14GHz signal by frequency multiplication link to 84GHz, the signal of 84GHz is 336GHz local oscillation signal by 4 frequency multiplier frequencys multiplication of frequency multiplication link, and the local oscillation signal of 336GHz is that the reflection of the smooth silicon chip of 10cm (beam splitter) enters Terahertz frequency mixer through having a super-hemispherical medium silicon lens by diameter.

Step 3: open high temperature blackbody radiation source, is adjusted to room temperature and 300K by source temperature; The Terahertz noise signal that high temperature blackbody radiation source produces, the having a super-hemispherical medium silicon lens that is transmitted through being the smooth silicon chip of 10cm (beam splitter) by diameter enters Terahertz frequency mixer; The intermediate-freuqncy signal that Terahertz frequency mixer produces successively through gain be the low noise amplifier (first order low noise amplifier) of 15dB, gain is the low noise amplifier (second level low noise amplifier) of 25dB, the bandpass filter ingoing power meter of centre frequency 1GHz bandwidth 200MHz.

Step 4: record the result that now power meter Agilent N1911A shows.

Step 5: high temperature blackbody source temperature is adjusted to high temperature 1473K.The Terahertz noise signal that high temperature blackbody radiation source produces, the having a super-hemispherical medium silicon lens that is transmitted through being the smooth silicon chip of 10cm (beam splitter) by diameter enters Terahertz frequency mixer; The intermediate-freuqncy signal that Terahertz frequency mixer produces successively through gain be the low noise amplifier (first order low noise amplifier) of 15dB, gain is the low noise amplifier (second level low noise amplifier) of 25dB, the bandpass filter ingoing power meter of centre frequency 1GHz bandwidth 200MHz.

Step 6: record the result that now power meter Agilent N1911A shows.

Step 7: the noise temperature calculating the quasi-optical receiver front end of heterodyne system Terahertz by the Y factor method improved is 12040K.

This analysis of test methods blackbody radiation characteristic of THz wave, improve traditional millimere-wave band the is similar to Planck's law of radiation theory of testing with Rayleigh-Jones's law, the more accurate theory of testing is obtained by carrying out Taylor expansion to Planck law, make the theory of testing more reasonable, method of testing is more perfect.

Above-mentioned example is only that protection scope of the present invention is not limited thereto in order to absolutely prove the preferably example that the present invention lifts.The equivalent replacement that those skilled in the art do on basis of the present invention or conversion, all in protection scope of the present invention.Protection scope of the present invention is as the criterion with claims.

Claims (3)

1. a noise temperature test macro for the quasi-optical receiver front end of heterodyne system Terahertz, is characterized in that: this system comprises that high temperature blackbody radiation source, frequency multiplier, microwave signal source, beam splitter, Terahertz quasi-optical frequency mixer, BLAS are biased, first order low noise amplifier, second level low noise amplifier, bandpass filter and power meter;

High temperature blackbody radiation emission Terahertz noise signal, Terahertz noise signal enters Terahertz quasi-optical frequency mixer through the part of beam splitter;

Microwave signal source launched microwave signal, microwave signal forms local oscillation signal through frequency multiplication link frequency multiplication after Terahertz frequency range, and local oscillation signal enters Terahertz quasi-optical frequency mixer through the part of beam splitter reflection;

The Terahertz noise signal and the local oscillation signal that enter into Terahertz frequency mixer carry out mixing, obtain intermediate-freuqncy signal after mixing, and the intermediate-freuqncy signal obtained is more successively through first order low noise amplifier, second level noise amplifier, bandpass filter and power meter.

2. the method for testing of the noise temperature of the quasi-optical receiver front end of heterodyne system Terahertz, is characterized in that step is:

(1) open the instrument of this test macro, carry out thermal pretreatment, the required function element in calibration, debugging and mounting test system and testing tool;

(2) by microwave signal source launch local oscillation signal through frequency multiplier frequency multiplication to Terahertz frequency range, enter Terahertz quasi-optical frequency mixer through beam splitter;

(3) the Terahertz noise signal produced under different radiation temperature by high temperature blackbody radiation source enters Terahertz quasi-optical frequency mixer through beam splitter, and two paths of signals carries out mixing and obtains intermediate-freuqncy signal in Terahertz quasi-optical frequency mixer;

(4) intermediate-freuqncy signal enters Computer display test result through low noise amplifier, bandpass filter, power meter;

(5) according to the method for Y factor, the noise temperature of the quasi-optical receiver front end of Terahertz is calculated.

3. the method for testing of the noise temperature of the quasi-optical receiver front end of heterodyne system Terahertz according to claim 2, is characterized in that:

The computing method of step (5) are:

The brightness B of Planck law _fformula:

$B_f=\frac{2{\mathrm{hf}}^3}{c^2}\left(\frac{1}{e^{\mathrm{hf}/\mathrm{kT}}-1}\right)---\left(1\right)$

Wherein, c is the light velocity, and h is Planck's constant, and k is Boltzmann constant, and f is frequency, and T is radiation temperature;

Order by e ^afcarry out Taylor expansion:

$e^{\mathrm{Af}}=1+\mathrm{Af}+\frac{1}{2}{A}^2{f}^2+\frac{1}{6}{A}^3{f}^3......---\left(2\right)$

The radiance B ' of the improvement that the first three items of getting expansion item obtains _fformula be:

$B_f^{\′}=\frac{2\mathrm{kT}}{{\mathrm{\λ}}^2}\left(\frac{2\mathrm{kT}}{2\mathrm{kT}+\mathrm{hf}}\right)---\left(3\right)$

Wherein, λ is wavelength;

According to Ruili Jones's law, an antenna is placed in the blackbody radiation environment that a temperature is T, and the noise power P that calculating antenna receives is:

$P=\frac{1}{2}{A}_r{\∫}_f^{f+\mathrm{\Δf}}\underset{4\mathrm{\π}}{\∫\∫}\frac{2\mathrm{kT}}{{\mathrm{\λ}}^2}{F}_n(\mathrm{\θ},\mathrm{\φ})\mathrm{d\Ωdf}---\left(4\right)$

If the Power Limitation detected is in an arrowband Δ f, then the radiance of black matrix approximate constant in Δ f;

By aerial radiation solid angle Ω _pfor:

$\underset{4\mathrm{\π}}{\∫\∫}{F}_n(\mathrm{\θ},\mathrm{\φ})\mathrm{d\Ω}={\mathrm{\Ω}}_p---\left(5\right)$

${\mathrm{\Ω}}_p=\frac{{\mathrm{\λ}}^2}{A_r}---\left(6\right)$

Wherein F _nthe normalization antenna pattern that (θ, φ) is antenna, n represents normalization, and θ represents the elevation angle, and φ represents position angle, A _rfor the effective radiating area of antenna;

Can draw according to formula (4)-(6):

P＝kTΔf (7)

At the power density P that millimeter wave band Ruili Jones's law calculates ^r-J:

P ^R-J＝k·T (8)

In Terahertz frequency range by the power density P ' obtained of correction formula be:

$P^{\′}=\mathrm{kT}\left(\frac{2\mathrm{kT}}{2\mathrm{kT}+\mathrm{hf}}\right)\≡{\mathrm{kT}}^{\′}---\left(9\right)$

In conjunction with to the definition of noise temperature namely: noise temperature is that the radiation power of single frequency obtains the define method to the noise temperature T ' improved with the ratio of Boltzmann constant and to the define method of noise power:

$T^{\′}=T\left(\frac{2\mathrm{kT}}{2\mathrm{kT}+\mathrm{hf}}\right)---\left(10\right)$

Obtain the corresponding noise temperature T of this test macro _rcomputing formula:

$T_R=\frac{T_{\mathrm{hot}}^{\′}-{\mathrm{YT}}_{\mathrm{cold}}^{\′}}{Y-1}---\left(11\right)$

Wherein, T ' _hotwith T ' _coldfor the high temperature after improvement and the cold and hot load temperature under low temperature, Y is the Y factor value recorded.