阅读说明：本技术 一种用于扩频的双端口平面谐波混频器 (Dual-port plane harmonic mixer for spread spectrum ) 是由 郭健 钱澄 于 2019-10-09 设计创作，主要内容包括：本发明公开一种用于扩频的双端口平面谐波混频器,包括射频带通滤波器、射频输入匹配电路、反向并联的肖特基二极管对、本振中频匹配电路和本振中频低通滤波器。本发明提供的谐波混频器,具有带宽宽、电路结构简单、可用纯平面微带电路实现、便于与其他平面电路集成的优点。本发明通过调整该电路中各个组成部分的参数,该结构适用于四次谐波混频以上的高次谐波混频,通过与频谱仪内置扩频本振结合,可以很方便的将微波频段频谱仪扩展到毫米波乃至太赫兹波段。(The invention discloses a dual-port plane harmonic mixer for spread spectrum, which comprises a radio frequency band-pass filter, a radio frequency input matching circuit, a Schottky diode pair connected in parallel in an opposite direction, a local oscillator intermediate frequency matching circuit and a local oscillator intermediate frequency low-pass filter. The harmonic mixer provided by the invention has the advantages of wide bandwidth, simple circuit structure, capability of being realized by a pure plane microstrip circuit and convenience for integration with other plane circuits. The structure is suitable for higher harmonic mixing above fourth harmonic mixing by adjusting the parameters of each component in the circuit, and can conveniently extend the microwave frequency band frequency spectrograph to millimeter wave and even terahertz wave bands by combining with a built-in spread spectrum local oscillator of the frequency spectrograph.)

1. A dual-port plane harmonic mixer for spread spectrum is characterized by comprising a radio frequency band-pass filter (1), a radio frequency input matching circuit (2), a reverse parallel Schottky diode pair (3), a local oscillator intermediate frequency matching circuit (4) and a local oscillator intermediate frequency low-pass filter (5);

The radio frequency band-pass filter (1) is located at a radio frequency input end, and is sequentially connected with a radio frequency input matching circuit (2), two reverse parallel Schottky diode pairs (3), a local oscillator intermediate frequency matching circuit (4) and a local oscillator intermediate frequency low-pass filter (5) and finally connected with a local oscillator/intermediate frequency port.

2. A two-port planar harmonic mixer for spread spectrum according to claim 1, wherein the rf band pass filter (1) provides dc ground, effectively rejecting local and intermediate frequency signals by inputting a wide band rf signal.

3. A two-port planar harmonic mixer for spread spectrum according to claim 1, characterized in that the rf band-pass filter (1) employs a filtering structure with grounded metallized holes.

4. A two-port planar harmonic mixer for spread spectrum according to claim 1, characterized in that the rf band-pass filter (1) is a parallel short-path wideband band-pass filter structure.

5. A dual-port planar harmonic mixer for spread spectrum according to claim 1 wherein the local oscillator if low pass filter (5) is a compact microstrip resonant cell structure.

Technical Field

The invention belongs to the technical field of plane harmonic mixing, and particularly relates to a dual-port plane harmonic mixer for spread spectrum.

Background

The spectrum analyzer is one of the important instruments for signal measurement, and German technology and Luode and Schwarz are two mainstream companies which can provide spectrum analyzers internationally. At present, the upper limit of the analysis frequency of the mainstream spectrometers provided by two companies is 26.5GHz and 50GHz, and recently, spectrum analyzers with the frequency up to 67GHz have been introduced. Of course, the higher the operating frequency of a spectrum analyzer, the more expensive it is.

In order to reduce the low cost requirement of the user for high frequency measurement, the spectrum analyzer generally has an option for frequency extension, and a local oscillator and an intermediate frequency interface are provided for externally connecting a harmonic mixer to extend the measurement frequency of the spectrum analyzer. For example, the German and scientific PXA series provides a spread spectrum SMA interface, the interface is a local oscillator and intermediate frequency shared interface, a local oscillator output is provided at the same time, an intermediate frequency input signal is received, a duplexer is arranged in the instrument to distinguish the two signals, and the local oscillator frequency range is 3.75-14.1 GHz. The frequency spectrograph with the single expansion interface is suitable for being matched with a two-port harmonic mixer to realize frequency expansion. The two-port mixer has only two physical interfaces, namely a radio frequency interface and a local oscillator/intermediate frequency shared interface. The FSW series of Rode and Schwarz provides three spread spectrum SMA interfaces, wherein one local oscillator/intermediate frequency shared interface similar to the PXA series is adapted to a dual-port harmonic mixer; and the other pair of independent local oscillator and intermediate frequency interfaces are adapted to the three-port harmonic mixer. The three-port harmonic mixer is a conventional harmonic mixer, and a radio frequency, a local oscillator and an intermediate frequency are respectively provided with a physical interface. The frequency range of local oscillation signals of the FSW series is 7.65-17.45 GHz, and is slightly higher than that of local oscillation signals of the PXA series. In addition, the working frequency band of the harmonic mixer is usually a standard waveguide frequency band, such as 26.5 to 40GHz, 33 to 50GHz, 50 to 75GHz, 75 to 110GHz, etc.

German technologies and two companies, rodd and schwarz, have also introduced a series of harmonic mixers to extend the measurement frequency of microwave spectrometers (e.g., up to 110GHz for a 26.5GHz spectrometer via a harmonic mixer). The 11970 series harmonic mixer in Germany is a three-port higher harmonic mixer and is adapted to an early spectrometer; the M1970 series intelligent harmonic mixer is a dual-port harmonic mixer and is suitable for PXA and newer series spectrometers. The FS-Z series harmonic mixer from Rode and Schwarz is a three-port mixer, adapted to its own FSW series spectrometer.

Although the use of harmonic mixers to perform high frequency measurements of a spectrometer has greatly reduced the cost as compared to purchasing a high frequency spectrometer directly, a single harmonic mixer is still expensive. For these harmonic mixer technologies, there is no disclosure of foreign instrument manufacturers, and it is very necessary to develop a reliable high-frequency harmonic mixer.

There are some reports at home and abroad on the high-order harmonic mixing technology applicable to the extension of the frequency spectrograph. These harmonic mixers are three-port harmonic mixers, and generally employ circuits of a three-dimensional structure. Hongwei (hongwei, millimeter wave harmonic mixer spread spectrum technology, electronic technology, 11 th 2003, pp55-56) reports a three-port millimeter wave harmonic mixer, which adopts a structure of combining a waveguide and a strip line, and directly places a diode in a waveguide cavity for coupling radio frequency signals. The xisanfang (xisanfang lin, a waveguide harmonic mixer, utility model, CN89213389.9, 1990.7.11) also introduced a three-port harmonic mixer based on a waveguide structure. Zhangbo et al (Zhangbo qian jun si meng jiao, a 340GHz eighth harmonic mixer, invention patent, CN201510514409.X, 2015.8.20) proposed a three-port mixer using a suspended microstrip line (three-dimensional) structure. Dingdlzhi et al (Dingdlzhi Xujin Ping Chenzhenhua, W-band broadband octa-harmonic mixer based on Schottky diode improved model, infrared and millimeter wave academy, volume 34 (3), 2015.6) propose a three-port harmonic mixer based on fin line conversion. Huang et al (Y. Huang, W. Hui and dB. Alderman, "A W Band Third-Harmonic Mixer Using Planar Mixer Diodes,"2018International Conference on Microwave and Millimeter Wave Technology (ICMM), Chengdu,2018, pp.1-3) also propose a Harmonic Mixer based on a waveguide three-dimensional structure. To summarize, the harmonic mixers reported are almost three-port mixers, mostly adopting a waveguide structure, and most harmonic mixers fail to operate in the whole waveguide frequency band.

Disclosure of Invention

The purpose of the invention is as follows: aiming at the problems in the prior art, the invention provides a dual-port plane harmonic mixer for spread spectrum, which has the advantages of simple structure, pure plane and convenient integration, and can be used for the broadband frequency extension of the existing mainstream frequency spectrograph.

The technical scheme is as follows: in order to solve the technical problem, the invention provides a dual-port plane harmonic mixer for spread spectrum, which comprises a radio frequency band-pass filter, a radio frequency input matching circuit, a reverse parallel Schottky diode pair, a local oscillator intermediate frequency matching circuit and a local oscillator intermediate frequency low-pass filter, wherein the radio frequency band-pass filter is connected with the radio frequency input matching circuit; and each component functional circuit of the planar harmonic mixer is of a planar microstrip structure.

the radio frequency band-pass filter is positioned at a radio frequency input end, and is sequentially connected with a radio frequency input matching circuit, two Schottky diode pairs in reverse parallel connection, a local oscillator intermediate frequency matching circuit and a local oscillator intermediate frequency low-pass filter, and is finally connected with a local oscillator/intermediate frequency port. It can be seen that the planar harmonic mixer has only two ports, namely, a radio frequency input port and a local oscillator/intermediate frequency common port.

Furthermore, the radio frequency band-pass filter provides a direct current ground by inputting a broadband radio frequency signal, and effectively inhibits a local oscillator and an intermediate frequency signal. The radio frequency band-pass filter can only pass full-band radio frequency signals and has a suppression effect on local oscillation and intermediate frequency signals, and the band-pass filter also has a function of providing signal loops (equivalent ground) for the local oscillation and the intermediate frequency signals; in addition, the radio frequency band-pass filter adopts a filtering structure with a grounding metalized hole, so that a direct current signal ground can be provided for the diode, and the effective work of the diode is ensured.

Furthermore, the radio frequency band-pass filter adopts a filtering structure with a grounding metalized hole.

Furthermore, the radio frequency band-pass filter adopts a parallel short-circuit line broadband band-pass filter structure.

Furthermore, the local oscillator intermediate frequency low pass filter adopts a compact microstrip resonance unit structure.

The low-pass filter can inhibit the full-band radio frequency signal through the local oscillator and the intermediate frequency signal, so that the low-pass filter also has the function of providing a radio frequency signal loop (equivalently).

The reverse parallel Schottky diode pair is widely used in the even harmonic mixer, and the local oscillator odd harmonic can be limited within the diode pair, so that the local oscillator odd harmonic can be effectively inhibited, and the frequency conversion loss of the harmonic mixer is reduced.

The radio frequency input matching circuit and the local oscillator intermediate frequency matching circuit are respectively positioned at two sides of the reverse parallel diode pair and used for input and output matching of the reverse parallel diode pair, and low-loss frequency conversion of a full-wave band frequency band is realized.

The invention relates to a plane harmonic mixer applied to a millimeter wave/terahertz frequency band, which only has two ports, namely a radio frequency port and a local oscillator/intermediate frequency shared port, does not need other equipment for assistance, and can be directly used for expanding the frequency of the existing mainstream spectrum analyzer (such as PXA series of Germany and technology and FSW series of Rode and Shiwa) from a microwave frequency band to a millimeter wave or even a terahertz frequency band.

Compared with the prior art, the invention has the advantages that: the plane harmonic mixer for spread spectrum provided by the invention is a dual-port harmonic mixer, has the advantages of simple structure, convenient assembly of a pure plane circuit and integration with other circuits, and low cost, and can be used for frequency extension of the existing mainstream frequency spectrograph.

Drawings

FIG. 1 is a schematic structural view of the present invention;

FIG. 2 is a diagram of a RF band pass filter model and simulation results in an embodiment;

FIG. 3 is a diagram illustrating simulation results of a local oscillator IF low-pass filter in an exemplary embodiment;

FIG. 4 is a diagram illustrating simulation results of frequency conversion loss of a W-band eighth harmonic mixer in an exemplary embodiment.

Detailed Description

The invention is further elucidated with reference to the drawings and the detailed description. The described embodiments of the present invention are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, other embodiments obtained by a person of ordinary skill in the art without any creative effort belong to the protection scope of the present invention.

As shown in fig. 1, a dual-port planar harmonic mixer for spread spectrum includes a radio frequency band pass filter 1, a radio frequency input matching circuit 2, a schottky diode pair 3 connected in reverse parallel, a local oscillator intermediate frequency matching circuit 4, and a local oscillator intermediate frequency low pass filter 5; the radio frequency band-pass filter 1 is located at a radio frequency input end, and is sequentially connected with a radio frequency input matching circuit 2, two Schottky diode pairs 3 in reverse parallel connection, a local oscillator intermediate frequency matching circuit 4 and a local oscillator intermediate frequency low-pass filter 5, and is finally connected with a local oscillator/intermediate frequency port.

the design of each unit circuit is specifically introduced by taking a W-band (WR-10 waveguide, the waveguide frequency band is 75-110 GHz) eight-harmonic mixer as an example, and the design is also effective for the mixers with other harmonic frequencies in other frequency bands.

The W-band eight-harmonic mixer can be matched with a German technology PXA or a newer series, a FSW series frequency spectrograph of the Shiwaz company is subjected to frequency expansion, the receiving intermediate frequency of the frequency mixer is lower than 1GHz, the corresponding local oscillation frequency range is about 9.5-13.625 GHz, and the receiving intermediate frequency is within the local oscillation frequency range provided by the two series frequency spectrometers. Of course, when designing a harmonic mixer of a certain frequency band, first, whether the local oscillation frequency required by the harmonic mixer is within the local oscillation frequency range provided by the instrument must be considered; if the local oscillator frequency is higher than the local oscillator frequency provided by the instrument, it is necessary to consider increasing the harmonic frequency of the harmonic mixer, thereby reducing the required local oscillator frequency to fall within the frequency range provided by the instrument.

The radio frequency band-pass filter 1 adopts a parallel short-circuit line broadband band-pass filter structure (G.L.Matthaei, L.Young and E.M.T.Jones, Microwave Filters, Impedance-Matching Networks, and connecting structures, Norwood, MA, USA: Aretech House,1985, pp.595-614.), and the structure has the advantages of wide bandwidth and small loss, and the parallel short-circuit line of the filter naturally provides direct current ground required by the diode. Fig. 2 shows a three-dimensional electromagnetic field simulation model and simulation results of the filter, and it can be seen from the simulation results that the bandwidth of the filter can meet the passband requirement of 75-110 GHz, and the suppression effect in the local oscillator and the intermediate frequency band is good.

the local oscillator intermediate frequency Low pass filter 5 adopts a CMRC (compact microstrip resonant cell) structure (q.xue, k.m.sum, and c.h.chan, "Low Conversion-less fourth harmonic Mixers Incorporating CMRC for Millimeter-Wave Applications," ieee trans micro thermal Tech, vol.51, No.3, pp.1449-1454,2003), and the structure has the advantages of compact structure, good impedance bandwidth and good out-of-band rejection. The invention adopts a two-stage CMRC structure to form a wide-stop-band low-pass filter, and a model and a simulation result (three-dimensional model simulation, in order to improve the accuracy of the simulation, mesh subdivision simulation is carried out in a segmented mode, and finally the simulation result is spliced together) of the wide-stop-band low-pass filter are shown in figure 3. Simulation results show that the cut-off frequency of the low-pass filter is 30GHz, and 75-110 GHz can be restrained by the medium frequency and the local oscillation signals by more than 25 dB.

In addition, when the mixer is designed, the reverse parallel schottky diode 3 needs to be modeled, and a three-dimensional electromagnetic field model is generally more accurate.

Finally, the S parameter obtained by simulating the three-dimensional electromagnetic field model of the radio frequency band-pass filter 1, the local oscillator intermediate frequency low-pass filter 5 and the Schottky diode pair 3 in reverse parallel is led into circuit simulation software (for example ADS of Germany and technology). The radio frequency input matching circuit 2 and the local oscillator intermediate frequency matching circuit 4 are respectively composed of two (or multiple) sections of microstrip transmission lines in the ADS, and the frequency conversion loss of the frequency mixer is optimized by adjusting the line width and the length of the microstrip lines, so that all final circuit parameters are obtained. Fig. 4 shows the simulation result of the final conversion loss of the harmonic mixer.