An on-chip low insertion loss dual-frequency transformer for terahertz harmonic extraction

Abstract

The present invention relates to a terahertz harmonic extraction technology, and in particular to an on-chip low insertion loss dual-frequency transformer for terahertz harmonic extraction, comprising a primary coil and a secondary coil stacked from bottom to top, wherein two ports of the primary coil are respectively a differential fundamental frequency signal and a positive phase fundamental frequency signal P in + and negative phase fundamental frequency signal P in The two ports of the secondary coil are the differential harmonic signal and the positive phase harmonic signal P out + and negative phase harmonic signal P out ‑output port; the primary coil and the secondary winding are a co-centered octagonal structure. The dual-frequency transformer can change the coupling degree between the primary and secondary coils by setting different inner diameters, so that the dual-frequency transformer presents high-pass filtering characteristics, thereby effectively extracting terahertz harmonic signals from high-frequency signals. It has the advantages of simple structure, small insertion loss, small size, and low manufacturing cost, and has extremely high application value in on-chip terahertz signal source generation circuits.

Description

Technical Field

[0001] The present invention belongs to the technical field of terahertz harmonic extraction, and in particular relates to an on-chip low-insertion-loss dual-frequency transformer for terahertz harmonic extraction. Background Art

[0002] Terahertz (THz) waves refer to electromagnetic waves in the range of 0.1THz to 10THz, with a corresponding wavelength of 10μm to 3mm. Due to its high penetration, strong spectral resolution and non-ionization characteristics, the application of terahertz spectrum in the fields of biomedical imaging, spectral analysis, human safety inspection, and communications has extremely important research value.

[0003] For terahertz systems, whether in communication or imaging applications, oscillation signal sources in the terahertz frequency band are required, so terahertz signal sources are the key to promoting the application of terahertz technology. In recent years, with the development of integrated circuits, the realization of low-cost, high-integration on-chip terahertz signal sources has received increasing attention. However, due to the maximum oscillation frequency f of the process device, max Due to the limitations of the oscillator, it is a considerable challenge to directly generate a terahertz signal source with low phase noise, precision and stability, and high output power through a fundamental frequency oscillator. In order to overcome the above limitations, harmonic extraction technology is usually used, that is, extracting terahertz harmonic signals from the high-frequency signal generated by the oscillator. However, the existing push-push harmonic extraction structure has the problems of complex design, high loss and low output power. Summary of the invention

[0004] In view of the problems existing in the background technology, the present invention provides an on-chip low insertion loss dual-frequency transformer for terahertz harmonic extraction.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solution: an on-chip low insertion loss dual-frequency transformer for terahertz harmonic extraction, comprising a primary coil and a secondary coil stacked from bottom to top, wherein the two ports of the primary coil are respectively a differential fundamental frequency signal and a positive phase fundamental frequency signal P in + and negative phase fundamental frequency signal P in - input port, the two ports of the secondary coil are differential harmonic signal and positive phase harmonic signal P out + and negative phase harmonic signal P out -output port; the primary coil and the secondary winding are a co-centric octagonal structure.

[0006] In the above-mentioned on-chip low insertion loss dual-frequency transformer for terahertz harmonic extraction, the primary coil is wound with the sub-top metal TM1, the line width is W1, the inner radius of the primary coil is R1, and the number of turns is 1; the tap lengths of the two input ports of the primary coil are both L1, and the spacing is D1.

[0007] In the above-mentioned on-chip low insertion loss dual-frequency transformer for terahertz harmonic extraction, the secondary coil is wound with the top metal TM2, with a line width of W2, an inner radius of the secondary winding of R2, and a number of turns of 1; the tap lengths of the two output ports of the secondary coil are both L2, and the spacing is D2.

[0008] In the above-mentioned on-chip low insertion loss dual-frequency transformer for terahertz harmonic extraction, the primary winding and the secondary coil adopt a partially overlapping structure, and R1>R2, the inner diameter 2R1 of the primary coil is larger than the inner diameter 2R2 of the secondary coil, and the width of the overlapping portion of the primary coil and the secondary winding is X.

[0009] Compared with the prior art, the present invention has the following beneficial effects:

[0010] 1) Good high-pass characteristics: Since the primary and secondary coils of the present invention adopt an incompletely overlapping structure, they have good high-pass characteristics and effectively attenuate the frequency components in the high-frequency signal that are lower than the target terahertz harmonic peak frequency to extract the target terahertz harmonic signal components.

[0011] 2) Low loss and good balance: The primary and secondary coils of the present invention are wound into a co-centered octagonal structure, which reduces substrate loss. The wire length of the metal layer is short, which reduces the insertion loss between the input and output ports. At the same time, the symmetry of the structure also optimizes the electromagnetic coupling (mutual inductance) between the coils, and improves the amplitude and phase balance performance of the output harmonic signal.

[0012] 3) Simple and compact structure and small size: The present invention is formed by stacking only two single-turn coils, which effectively simplifies the complexity of the passive electromagnetic structure design and makes the on-chip layout compact.

[0013] 4) Good compatibility of manufacturing process: The primary and secondary coils of the present invention are wound with only two layers of metal, the sub-top metal and the top metal. Usually, integrated circuit manufacturing processes such as silicon-based processes CMOS / SiGe BiCMOS and III-V compound processes GaN / GaAs can provide relevant metal layers for design. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A schematic plan view of an on-chip low insertion loss dual-frequency transformer for terahertz harmonic extraction according to an embodiment of the present invention;

[0015] Figure 2 A cross-sectional view of an on-chip low insertion loss dual-frequency transformer for terahertz harmonic extraction along the AA' direction according to an embodiment of the present invention;

[0016] Figure 3 The S of an on-chip low insertion loss dual-frequency transformer for terahertz harmonic extraction according to an embodiment of the present invention is 21 Simulation curve;

[0017] Figure 4 This is a spectrum diagram of a terahertz third harmonic signal extracted by an on-chip low insertion loss dual-frequency transformer for terahertz harmonic extraction according to an embodiment of the present invention. DETAILED DESCRIPTION

[0018] The technical solutions in the embodiments of the present invention will be described clearly and completely below in combination with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0020] The present invention will be further described below in conjunction with specific embodiments, but the present invention is not limited thereto.

[0021] In order to solve the problems of complex design, high loss and low output power of the existing push-push harmonic extraction structure, the dual-frequency transformer in this embodiment can adopt a Balun connection method to increase the output power of the harmonic signal. Its passive electromagnetic structure is wound by the metal layer in the integrated circuit process, and is less affected by the power supply noise, temperature and process (PVT) changes of the process, and has low noise. It also has the characteristics of small insertion loss, simple and compact structure and small area. Therefore, it can be widely used in the harmonic generation circuit of the on-chip terahertz signal source.

[0022] This embodiment is realized by the following technical solution: an on-chip low insertion loss dual-frequency transformer for terahertz harmonic extraction, comprising from bottom to top: a primary coil and a secondary coil, which are co-centered octagonal structures. The two ports of the primary coil are differential baseband signals and positive phase baseband signals P in + and negative phase fundamental frequency signal P in - input port, the two ports of the secondary coil are differential harmonic signal positive phase harmonic signal P out + and negative phase harmonic signal P out - output port. The dual-frequency transformer exhibits high-pass filtering characteristics to effectively filter out the positive-phase fundamental frequency signal P in + and negative phase fundamental frequency signal P in -The frequency component below the target terahertz harmonic peak frequency is obtained, thereby achieving the target terahertz harmonic signal positive phase harmonic signal P out + and negative phase harmonic signal P out -Extraction.

[0023] The primary coil is wound with the sub-top metal TM1, with a line width of W1, an inner radius of the primary coil of R1, and a number of turns of 1. The tap lengths of the two input ports of the primary coil are both L1, and the spacing is D1.

[0024] The secondary coil is wound with the top metal TM2, with a line width of W2, an inner radius of the secondary coil of R2, and a number of turns of 1. The tap lengths of the two output ports of the secondary coil are both L2, and the spacing is D2.

[0025] The primary coil and the secondary coil adopt a partially overlapping structure, and R1>R2, the inner diameter 2R1 of the primary coil is larger than the inner diameter 2R2 of the secondary coil, and the width of the overlapping portion of the primary coil and the secondary coil is X.

[0026] The working principle of this embodiment is as follows: a differential high-frequency signal P including fundamental wave components and harmonic wave components in + and P in -Through the input port of the transformer primary coil, the primary coil converts the differential high-frequency signal P in + and P in - coupled to the secondary coil, after high-pass filtering, the secondary coil attenuates the differential high-frequency signal P in + and P in -The spectrum components below the cutoff frequency are extracted to extract the terahertz harmonic signal component P out + and P out -, and output through the output port. This embodiment works in a dual-frequency state, that is, the primary coil inputs a differential high-frequency signal P in + and P in - is f0, and the secondary coil outputs the extracted terahertz harmonic signal P out + and P out - is the second harmonic 2f0 or the third harmonic 3f0; at the same time, the primary winding and the secondary coil can achieve impedance matching at the input and output ports.

[0027] This embodiment is a dual-frequency transformer. As a high-order resonant network, the impedance frequency response of the transformer can theoretically have multiple resonant peak points. For a transformer, without considering the coupling mutual inductance between the two coils, the resonant frequencies of the primary coil and the secondary coil self-inductance can be expressed as:

[0028]

[0029]

[0030] Where L P and L S are the self-inductance of the primary coil and the secondary coil, respectively, C P and C Sare the parasitic capacitances of the primary coil and the secondary coil, respectively. Different from the conventional single-frequency transformer, the primary coil and the secondary coil of this embodiment use different metal layers and are designed to have different primary winding inner radii R1 and secondary winding inner radii R2, so ω P ≠ω S At this time, the transformer impedance frequency response curve Z 11 It can be observed that there are two different resonance peak points. 21 The same result will be found for the curves.

[0031] If the coupling between the coils is considered, the frequency magnitudes at the two resonance peak points can be expressed by the following equation (3):

[0032]

[0033] In the above formula, ω L is the low frequency peak point, ω H is the high frequency peak point, and k is the coupling coefficient. The expression of ξ is:

[0034]

[0035] By observing equations (3) and (4), it can be found that the magnitude of the two resonant peak frequencies is mainly determined by the coupling coefficient k of the transformer and the self-inductance and parasitic capacitance of the two coils. By adjusting the size of the two coils to change the magnitude of the self-inductance and parasitic capacitance and by adjusting the size of the overlapping area between the coils to change the degree of coupling, 1)ω L Near the target harmonic frequency to be extracted, the harmonics smaller than ω are attenuated. L The frequency component of H Much larger than ω L , and the corresponding gain peaks are equal, at this time the transformer gain curve S 21 It is flat between the two gain peaks, thus presenting a high-pass filtering characteristic.

[0036] In this embodiment, the primary coil and the secondary coil are designed as a co-centric octagonal structure to reduce substrate loss. The size of the overlapping area can be adjusted by setting different inner diameters to change the degree of coupling between the primary and secondary coils, so that the dual-frequency transformer exhibits high-pass filtering characteristics, thereby effectively extracting terahertz harmonic signals from high-frequency signals.

[0037] When implementing it, Figure 1 As shown in FIG. 1 , a schematic diagram of the on-chip low insertion loss dual-frequency transformer for terahertz harmonic extraction in this embodiment is shown, which includes, from bottom to top: a primary coil and a secondary coil, which are co-centered octagonal structures. The two ports of the primary coil are differential baseband signals and positive phase baseband signals P in + and negative phase fundamental frequency signal Pin - input port, the two ports of the secondary coil are differential harmonic signal positive phase harmonic signal P out + and negative phase harmonic signal P out - Output port.

[0038] Moreover, the primary coil is wound with the sub-top metal TM1, with a line width of W1 = 4 μm, an inner diameter of 2R1 = 28 μm, and a number of turns of 1. The tap lengths of the two input ports of the primary coil are both L1 = 10 μm, and the spacing is D1 = 8.5 μm.

[0039] Moreover, the secondary coil is wound with the top metal TM2, with a line width of W2=4μm, an inner diameter of 2R2=32μm, and a turn number of 1. The tap lengths of the two output ports of the secondary coil are both L2=12μm, and the spacing is D2=6.9μm.

[0040] like Figure 2 As shown, it is a cross-sectional view of the on-chip low insertion loss dual-frequency transformer for terahertz harmonic extraction in this embodiment along the AA' direction, and its process structure from bottom to top is: substrate layer (Substrate), sub-top metal layer TM1, top metal layer TM2. The thickness of the substrate layer is 300μm, the height from the top of the substrate layer to the bottom of the sub-top metal layer TM1 is 8.72μm, the thickness of the sub-top metal layer TM1 is 1.42μm, the height from the top of the sub-top metal layer TM1 to the bottom of the top metal layer TM2 is 5.52μm, and the thickness of the top metal layer TM2 is 4μm; the width of the overlapping part of the sub-top metal layer TM1 and the top metal layer TM2 is X=2μm.

[0041] like Figure 3 As shown, the S of the on-chip low insertion loss dual-frequency transformer for terahertz harmonic extraction in this embodiment is shown. 21 In the simulation curve, the fundamental wave f0 of the input signal is 100 GHz, the second harmonic 2f0 is 200 GHz, and the third harmonic 3f0 is 300 GHz. L Tuning to the vicinity of the third harmonic 3f0 (300GHz), the frequency components less than 300GHz, such as the fundamental wave f0 (100GHz) and the second harmonic 2f0 (200GHz), will be attenuated, realizing the extraction of the terahertz third harmonic 3f0 (300GHz); H Tuned to the vicinity of the fifth harmonic 5f0 (500GHz), and the corresponding gain peak is roughly equal to the gain peak of the third harmonic 3f0 (300GHz), then S 21 The curve is relatively flat in the frequency range of 300GHz to 500GHz, and the insertion loss is less than 2dB, showing good low insertion loss high-pass filtering characteristics. At 300GHz, the insertion loss is only 0.9dB.

[0042] like Figure 4 As shown in the figure, the spectrum of the terahertz third harmonic signal extracted by the on-chip low insertion loss dual-frequency transformer for terahertz harmonic extraction in this embodiment is shown. The signal power at the third harmonic 300GHz is -9.08dBm, and the signal power at the fundamental wave 100GHz and the second harmonic 200GHz are attenuated to -43.18dBm and -43.29dBm respectively, which are well suppressed; due to the high-pass characteristics, the signal power at the fourth harmonic 400GHz and the fifth harmonic 500GHz remain basically unchanged, which are: -26.82dBm and -34.31dBm respectively. Figure 4 The simulation results show that this embodiment successfully realizes the extraction of the terahertz third harmonic 300GHz signal with a large output power.

[0043] In summary, the embodiment provides an on-chip low insertion loss dual-frequency transformer for terahertz harmonic extraction, which can extract a high-output power terahertz third harmonic signal (about 300GHz) from a high-frequency signal with a fundamental wave of 100GHz. It has the advantages of good high-pass characteristics, low loss, high balance, simple structure, small size and good process compatibility, and has broad application prospects in on-chip terahertz signal source generation circuits.

[0044] The above are only preferred embodiments of the present invention, and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the contents of the specification of the present invention should be included in the protection scope of the present invention.

Claims

1. An on-chip low insertion loss dual-frequency transformer for terahertz harmonic extraction, characterized in that: It includes a primary coil and a secondary coil stacked from bottom to top, and the two ports of the primary coil are respectively a differential baseband signal and a positive phase baseband signal (P in +) and negative phase fundamental frequency signal (P in -) input port, and the two ports of the secondary coil are differential harmonic signal and positive phase harmonic signal (P out +) and negative phase harmonic signals (P out -) output port; the primary winding and the secondary coil adopt a partially overlapping structure, the inner radius of the primary coil is R1, and the number of turns is 1; the inner radius of the secondary winding is R2, and the number of turns is 1; and R1>R2, the inner diameter 2R1 of the primary coil is larger than the inner diameter 2R2 of the secondary coil, and the width of the overlapping part of the primary coil and the secondary winding is X.

2. The on-chip low insertion loss dual-frequency transformer for terahertz harmonic extraction according to claim 1, characterized in that: The primary coil is wound with the sub-top metal TM1, and its line width is W1. The tap lengths of the two input ports of the primary coil are both L1, and the spacing is D1.

3. The on-chip low insertion loss dual-frequency transformer for terahertz harmonic extraction according to claim 1, characterized in that: The secondary coil is wound with the top metal TM2, and its line width is W2. The tap lengths of the two output ports of the secondary coil are both L2, and the spacing is D2.

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