A high-integration broadband terahertz source

Abstract

The application discloses a high-integration wideband terahertz source, comprising a fundamental frequency source module and a frequency multiplication and power synthesis module, wherein the fundamental frequency source module comprises a single-chip microcomputer, a switch, a frequency and phase discriminator, an active low-pass loop filter, a voltage-controlled oscillator, a frequency divider and a power amplifier; the frequency multiplication and power synthesis module comprises a channel switch, a plurality of frequency multiplication channels and a frequency selection surface, and the terahertz wave output of the full frequency band of 0.1-10 THz is realized.

Description

Technical Field

[0001] This invention relates to the field of terahertz signal generation, and more specifically to a highly integrated broadband terahertz source. Background Technology

[0002] Terahertz waves are electromagnetic waves with frequencies ranging from 0.1 THz to 10 THz, possessing electromagnetic properties that combine those of microwaves and infrared radiation. Due to their unique penetrability, non-ionization, and spectral characteristics, they hold immense application potential in areas such as security inspection, biomedical imaging, 6G communication, and the detection of cultural relics and materials.

[0003] There are two main methods for generating terahertz signals: optical and electronic. Optical methods include gas-pumped lasers, terahertz parametric oscillators, and terahertz quantum cascade lasers. However, these methods suffer from drawbacks such as poor power stability, low conversion efficiency, and large device size. Electronic methods include vacuum electronics and solid-state semiconductors. Vacuum electronics suffers from drawbacks such as large size, the need for high-voltage control, and low integration density. Therefore, solid-state semiconductor technology is currently the more commonly used method for generating terahertz signals.

[0004] Solid-state semiconductor electronics technology mainly includes two types: resonant tunneling terahertz oscillators (RTDs) and solid-state frequency multipliers. RTDs, when combined with external circuitry, can directly generate terahertz signals. However, RTDs have low output terahertz power and operate at a single frequency. Solid-state frequency multipliers utilize nonlinear effects such as Schottky diodes to multiply microwave signals and output terahertz signals with a specific bandwidth. Multiple cascaded frequency multipliers can be used to multiply microwave signals to the terahertz band. However, terahertz signal generation based on solid-state electronics can only operate at a single frequency or output narrowband signals, greatly limiting the application scenarios of terahertz technology. Therefore, there is an urgent need for a highly integrated broadband terahertz source capable of generating arbitrary frequencies. Summary of the Invention

[0005] The summary section of this invention provides a brief overview of the concepts, which will be described in detail in the detailed description section below. This summary section is not intended to identify key or essential features of the claimed technical solutions, nor is it intended to limit the scope of the claimed technical solutions.

[0006] This invention proposes a highly integrated broadband terahertz source to solve one or more of the technical problems mentioned in the background section above.

[0007] This invention provides a highly integrated broadband terahertz source, comprising: a base frequency source module, which includes a microcontroller, a switch, a frequency and phase detector, an active low-pass loop filter, a voltage-controlled oscillator, a frequency divider, and a power amplifier; wherein, the switch is used to select an on-board temperature-controlled crystal oscillator or an external signal as the reference source for the base frequency source module; the microcontroller is used to communicate with a host computer to receive serial communication information, including frequency modulation codes and waveform adjustment codes; the microcontroller is also used to convert the frequency modulation codes and waveform adjustment codes into control signals suitable for the base frequency source module; the frequency and phase detector integrates a register and a charge pump; the voltage signal generated by the charge pump is amplified and filtered by the active low-pass loop filter, and then the frequency signal is obtained by the voltage-controlled oscillator; the frequency signal is divided into two paths, one of which is amplified by the power amplifier and used as the base frequency signal to be input to the frequency multiplication and power synthesis module, and the other path first passes through the first filter. After removing the second harmonic component, the signal is divided by two by a frequency divider, and then a second filter is used to remove potential harmonic components. The filtered output signal is used as the input of a frequency and phase detector. The frequency multiplication and power combining module includes a channel switch, multiple frequency multiplication channels, and a frequency selection surface. The bandwidth of the terahertz signal generated by each of the multiple frequency multiplication channels is different. The channel switch is used to feed the fundamental frequency signal of different signal periods into different frequency multiplication channels. Each of the multiple frequency multiplication channels includes a filter, an amplifier, a frequency multiplier, and a power divider. The filter is used to select a specific fundamental frequency signal, the amplifier is used to amplify the input fundamental frequency signal, the frequency multiplier is used to generate a terahertz wave of a specific frequency band, and the power divider is used to combine the terahertz waves of different frequency bands, outputting a full-band terahertz wave and inputting it into the frequency selection surface. The frequency selection surface is used to output a terahertz signal with a specified frequency and bandwidth.

[0008] Optionally, the reference source is split into two paths by a switch. One path is reserved to output a 100 MHz clock signal, which can be used by other parts of the system as the total clock signal. The other path is input to the frequency and phase detector as a reference signal.

[0009] Optionally, the highly integrated broadband terahertz source further includes a data acquisition system, which is used to acquire signals reflected by the detected target.

[0010] Optionally, the time sequence of the channel switch and the data acquisition system is controlled by a switch control circuit, so that the data acquisition system starts sweeping from the position where the first frequency multiplier channel begins to sweep and ends when the last frequency multiplier channel is completed.

[0011] This invention offers the following advantages: It can generate a broadband baseband signal of 8-20 GHz through a baseband source module, while exhibiting excellent signal linearity. Furthermore, in terms of timing, it employs a time-frequency division method between different periods of the baseband signal, generating multi-subband terahertz signals through frequency multiplication and power combining modules, thus reducing the requirements for broadband hardware. Finally, a power divider is used to combine the power to achieve a full-band terahertz wave output of 0.1-10 THz, and a specified terahertz frequency can be achieved through a frequency selection surface at the back end. Compared to existing terahertz signal generation methods, the terahertz source of this invention has higher integration and the ability to output multi-modulated full-band terahertz waves. Attached Figure Description

[0012] The above and other features, advantages, and aspects of the various embodiments of the present invention will become more apparent from the accompanying drawings and the following detailed description. Throughout the drawings, the same or similar reference numerals denote the same or similar elements. It should be understood that the drawings are schematic, and elements are not necessarily drawn to scale.

[0013] Figure 1 This is an exemplary structural diagram of the fundamental frequency source module included in a highly integrated broadband terahertz source according to the present invention. Figure 2 This is an exemplary structural diagram of a frequency doubling and power combining module included in a highly integrated broadband terahertz source according to the present invention. Figure 3 This is a signal schematic diagram of a frequency multiplication and power combining module included in a highly integrated broadband terahertz source of the present invention. Figure 4 The time-frequency curve of the measured broadband fundamental frequency source signal is shown. Figure 5 It is a time series diagram of frequency sweep synchronization signal, switch switching, and data acquisition. Detailed Implementation

[0014] The invention will now be described in more detail with reference to the accompanying drawings. While some embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the invention. It should be understood that the drawings and embodiments of the invention are for illustrative purposes only and are not intended to limit the scope of protection of the invention.

[0015] It should also be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings. Unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0016] It should be noted that the concepts of "first" and "second" mentioned in this invention are only used to distinguish different devices, modules or units, and are not used to limit the order of functions performed by these devices, modules or units or their interdependencies.

[0017] It should be noted that the terms "a" and "a plurality of" used in this invention are illustrative rather than restrictive. Those skilled in the art should understand that, unless otherwise expressly indicated in the context, they should be understood as "one or more".

[0018] The names of messages or information exchanged between the various devices of this invention are for illustrative purposes only and are not intended to limit the scope of these messages or information.

[0019] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0020] like Figure 1 As shown, the baseband source module includes a microcontroller 101, a switch 102, a frequency and phase detector 103, an active low-pass loop filter 104, a voltage-controlled oscillator 105, a frequency divider 106, and a power amplifier 107. The switch 102 is used to select either an onboard temperature-controlled crystal oscillator (100MHz) or an external signal as the reference source for the baseband source module. The microcontroller 101 is used to communicate with a host computer to receive serial communication information, including frequency modulation codes and waveform adjustment codes. The microcontroller 101 is also used to convert the frequency modulation codes and waveform adjustment codes into control signals suitable for the baseband source module. Specifically, the microcontroller 101 can convert the frequency modulation codes and waveform adjustment codes according to preset conversion rules or logic to obtain the aforementioned control signals. The frequency and phase detector 103 integrates a register and a charge pump. The voltage signal generated by the charge pump is amplified and filtered by an active low-pass loop filter 104, and then the frequency signal is obtained by a voltage-controlled oscillator 105. The frequency signal is divided into two paths. One path is a power amplifier 107 and used as the base frequency signal to be input to the frequency multiplication and power synthesis module. The other path first passes through a first filter 108 to remove the second harmonic component, then passes through a frequency divider 106 for frequency division by two, and then passes through a second filter 109 to remove potential harmonic components. The filtered output signal is used as the input of the frequency and phase detector 103.

[0021] In this invention, given that the voltage-controlled oscillator (VCO) has a wide tuning voltage range that exceeds the chip's power supply voltage, an active low-pass loop filter is used to amplify and filter the voltage signal output by the frequency and phase detector. Then, by (tuning) the VCO, the input voltage of chips with different power supply voltages can be controlled. The principle is filtering to output a specified voltage control range.

[0022] The aforementioned fundamental frequency source module can generate a fundamental frequency signal of 8-20 GHz. Specifically, the output frequency range can be controlled by adjusting the input voltage of the voltage-controlled oscillator (VCO). This invention employs a phase-locked loop (PLL) to compare the phase of the crystal oscillator with the phase of the VCO output signal in a phase-frequency discriminator. Through negative phase feedback, it achieves frequency signal output with excellent linearity. Simultaneously, as... Figure 4 As shown, the time-frequency curve of the baseband signal is displayed, which demonstrates that the baseband source module of the present invention has excellent signal linearity.

[0023] like Figure 2 As shown, the frequency multiplication and power combining module 200 includes a channel switch 201, multiple frequency multiplication channels 202, and a frequency selection surface 203. The bandwidth of the terahertz signal generated by each of the multiple frequency multiplication channels is different. The channel switch is used to feed the fundamental frequency signal with different signal periods into different frequency multiplication channels. Each of the multiple frequency multiplication channels includes a filter, an amplifier, a frequency multiplier, and a power divider. The filter is used to screen a specific fundamental frequency signal, the amplifier is used to amplify the input fundamental frequency signal, the frequency multiplier is used to generate a terahertz wave in a specific frequency band, and the power divider is used to combine the terahertz waves in different frequency bands to output a full-band terahertz wave and input it into the frequency selection surface. The frequency selection surface is used to output a terahertz signal with a specified frequency and bandwidth.

[0024] The frequency multiplication is primarily achieved through nonlinear devices (frequency multipliers). In these nonlinear components, due to nonlinear effects, harmonics are generated from the input fundamental frequency signal. These harmonics are integer multiples of the original frequency, such as second and third harmonics. Optionally, specific harmonic frequencies, such as second or third harmonics, can be selectively amplified using filters and amplifiers, thus generating terahertz signals through cascaded multipliers.

[0025] Specifically, assume the voltage of the input signal to the frequency multiplier is... The generated current is Taylor series expansion yields:

[0026] in, Indicates the input voltage. It is a constant that describes nonlinear characteristics.

[0027] If the input signal is a sine wave, that is Then the current can be expressed as:

[0028] in, It is the amplitude. For time, Let be the angular frequency of each harmonic. From the trigonometric identity expansion, we can see that... .

[0029] It can be seen that the output current contains multiple frequency components, namely the fundamental frequency and harmonics. This basic nonlinear relationship illustrates that when a sinusoidal signal passes through a nonlinear element, the output signal will contain the original frequency and its integer multiples, and subsequent filtering can obtain the corresponding frequency information. Then, a power divider combines the terahertz waves of different frequency bands to ultimately output a full-band terahertz wave. Finally, a frequency-selective surface outputs a terahertz signal with a specified frequency and bandwidth.

[0030] In some embodiments, the present invention can generate a broadband baseband signal of 8-20 GHz through a baseband source module, while exhibiting excellent signal linearity. Furthermore, in terms of timing, a time-division and frequency-division method is employed between different periods of the baseband signal. Multi-subband terahertz signals are generated through frequency multiplication and power combining modules, reducing the requirements for broadband hardware. Finally, a power divider is used for power combining to achieve a full-band terahertz wave output of 0.1-10 THz, and a specified terahertz frequency can be achieved through a frequency selection surface at the back end. Compared to existing terahertz signal generation methods, the terahertz source of the present invention has higher integration and multi-modulation full-band terahertz wave output.

[0031] Further reference Figure 3 , Figure 3 This is a signal schematic diagram of the frequency multiplication and power combining module. It shows how a baseband signal of 8-20 GHz is supplied sequentially to channel 1, channel 2, channel 3, ..., channel n via channel switches. Each frequency multiplication channel generates a terahertz signal with a different bandwidth. These signals are emitted via the frequency multiplier, radiating into free space to detect targets. All channels transmit signals based on time-division frequency-division multiplexing. Subsequently, the reflected terahertz signal is detected by the antenna in the frequency multiplication and power combining module (e.g., ...). Figure 2 (As shown by the black triangle in the middle) The signal is captured and converted into an intermediate frequency (IF) signal. Subsequently, these IF signals are switched via channel switches and collected by a data acquisition system (hereinafter referred to as data acquisition).

[0032] The timing sequence of channel switching operations and data acquisition is controlled by a dedicated switching control circuit, ensuring that data acquisition starts from the beginning of the frequency sweep of channel 1 and ends when the frequency sweep of channel n is completed, and then immediately enters the next acquisition cycle. Figure 5 This diagram displays the time series of the frequency sweep synchronization signal, switch transitions, and data acquisition. It clearly shows that only the rising edge of the frequency sweep synchronization signal is valid; each rising edge represents the completion of one frequency sweep and signifies that the switch will move to the next channel. Once all channels have finished switching, the data acquisition signal will generate a rising edge, marking the start of data acquisition.

[0033] Further reference Figure 5 As can be clearly seen from the diagram, only the rising edge of the frequency sweep synchronization signal is valid. Each rising edge represents the completion of one frequency sweep and signifies that the switch will move to the next channel. Once all channels have been switched, the data acquisition signal will generate a rising edge, marking the start of data acquisition.

[0034] The above description is merely a selection of preferred embodiments of the present invention and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention is not limited to specific combinations of the above-described technical features, but also includes other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the inventive concept. For example, technical solutions formed by substituting the above-described features with (but not limited to) technical features with similar functions disclosed in this invention.

Claims

1. A highly integrated broadband terahertz source, characterized in that, include: The baseband source module includes a microcontroller, a switch, a frequency and phase detector, an active low-pass loop filter, a voltage-controlled oscillator, a frequency divider, and a power amplifier. The switch selects either an onboard temperature-controlled crystal oscillator or an external signal as the baseband source. The microcontroller communicates with a host computer to receive serial communication information, including frequency modulation codes and waveform adjustment codes. The microcontroller also converts these codes into control signals suitable for the baseband source module. The frequency and phase detector integrates a register and a charge pump. The voltage signal generated by the charge pump is amplified and filtered by the active low-pass loop filter, and then passed through the voltage-controlled oscillator to obtain a frequency signal. This frequency signal is divided into two paths: one path, after passing through the power amplifier, serves as the baseband signal and is input to the frequency multiplication and power synthesis module; the other path first passes through a first filter to remove second harmonic components, then through the frequency divider for frequency division by two, and finally through a second filter to remove potential harmonic components. The filtered output signal serves as the input to the frequency and phase detector. The frequency multiplication and power combining module includes a channel switch, multiple frequency multiplication channels, and a frequency selection surface. Each frequency multiplication channel generates a terahertz signal with a different bandwidth. The channel switch feeds the fundamental frequency signal of different signal periods into different frequency multiplication channels. Each frequency multiplication channel includes a filter, an amplifier, a frequency multiplier, and a power divider. The filter filters a specific fundamental frequency signal, the amplifier amplifies the input fundamental frequency signal, the frequency multiplier generates a terahertz wave in a specific frequency band, and the power divider combines the terahertz waves of different frequency bands to output a full-band terahertz wave, which is then input to the frequency selection surface. The frequency selection surface outputs a terahertz signal with a specified frequency and bandwidth. The reference source is split into two paths by a switch. One path is reserved to output a 100 MHz clock signal, which can be used as the total clock signal for other parts of the system. The other path is input to the frequency and phase detector as a reference signal. The highly integrated broadband terahertz source also includes: A data acquisition system is used to acquire signals reflected by a detected target; the channel switch and the time sequence of the data acquisition system are controlled by a switch control circuit so that the data acquisition system starts sweeping the frequency from the time point of the first frequency doubling channel and ends at the time point of the completion of the frequency sweep of the last frequency doubling channel.

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