CN105141310B - Polycyclic broadband low phase noise frequency synthesizer - Google Patents

Abstract

The invention discloses a multi-ring broadband low-phase noise frequency synthesizer, which belongs to the microwave/millimeter wave field and can be applied to wide-band test instruments. The realization method of the multi-loop broadband low-phase noise frequency synthesizer is based on the traditional multi-loop phase-locked frequency synthesis structure, and the coarse tuning loop is replaced by the same frequency mixing structure as the addition loop from the traditional integer frequency division phase-locked loop Phase-locked loop, and added comb spectrum generator module to provide low phase noise input mixing signal to achieve better phase noise performance, while using frequency multiplier, frequency divider and DDS to expand the output frequency range . The method can replace the performance of the YIG oscillator in the broadband instrument, and has the characteristics of low phase noise, low spur, low power consumption, low cost and wide frequency band.

Description

Multi-loop Broadband Low Phase Noise Frequency Synthesizer

technical field

The invention belongs to the technical field of microwave/millimeter wave devices, relates to a wide-band test instrument, in particular to a multi-ring wide-band low-phase noise frequency synthesizer.

Background technique

Wireless communication test instruments mainly include vector signal sources, spectrum analyzers, vector network analyzers, channel simulators, etc. These test instruments have been monopolized by developed countries such as Europe and the United States for a long time. Frequency synthesis technology is an important part of these communication instruments, and its output frequency range and phase noise performance directly determine the performance index of the system. Therefore, the method of frequency synthesizer with wide frequency band, low phase noise, low cost and low spur is particularly important.

The wireless channel simulator is a test instrument that can simulate the path loss, fast fading, slow fading, delay spread, Doppler spread, noise and interference of the wireless channel indoors. The broadband frequency synthesizer is the core component of the test instrument , its performance index directly affects the performance index of the multi-antenna channel simulator.

The invention proposes a design method of a multi-ring wide-band low-phase noise frequency synthesizer, which can replace the YIG oscillator in the traditional instrument, and has low power consumption, low cost, low phase noise, low spurious, and easy integration The advantages.

Contents of the invention

Purpose of the invention: the frequency synthesizer is the most important component in the microwave communication instrument. The present invention proposes a method for realizing a multi-ring broadband low-phase noise frequency synthesizer. The method has the advantages of low phase noise, broadband, and low spurious Features, can greatly reduce the cost and power consumption of the instrument.

The invention provides a multi-ring broadband low-phase noise frequency synthesizer. The main technical solutions are as follows:

1) An implementation method applied to a multi-loop broadband frequency synthesizer, the main body of the method adopts a multi-loop frequency synthesis structure of a frequency mixing phase-locked loop, and the output frequency range is determined by the addition loop module, and the output frequency range of the addition loop module is 3~6GHz, and then expand the frequency range to 0.375~18GHz through the frequency multiplier and frequency divider, and the low frequency part of the 0.001~0.375GHz frequency band is output by the DDS with a reference clock of 1GHz. Finally, the 0.001~18GHz required by the index is realized. output frequency range.

2) An implementation method applied to a multi-loop broadband frequency synthesizer. The output frequency resolution of the multi-loop structure is equal to the output frequency resolution of the fine-tuning loop module. The fine-tuning loop module uses a fractional frequency division phase-locked loop, and the phase detection frequency 50MHz, using a 48-bit fractional frequency divider, the fractional frequency division PLL output frequency resolution is 1.78×10 ^-7 Hz, and after passing through a frequency divider with a frequency division ratio of 12, the resolution reaches 1.48×10 ^-8 Hz , after frequency multiplication and frequency division by the frequency expansion module, within the output frequency range, its frequency resolution can still reach 0.0001Hz.

3) an implementation method applied to a multi-ring broadband frequency synthesizer, characterized in that the method includes a reference loop, a fine tuning loop, a rough tuning loop, an addition loop, a comb spectrum generator module and a frequency extension module.

4) The difference between the coarse tuning loop and the traditional multi-loop solution lies in the addition of a mixing circuit and a DAC control circuit. The coarse tuning loop adopts a frequency mixing phase-locked loop structure, and its input reference frequency is 125MHz, 250MHz, 375MHz and 500MHz generated by the reference loop, and the mixing input frequency is generated by a comb spectrum generator module There are seven frequency points of 3GHz, 3.5GHz, 4GHz, 4.5GHz, 5GHz, 5.5GHz and 6GHz. The coarse tuning loop module adds these two sets of input frequencies to obtain an output frequency of 3-6GHz with a frequency step of 125MHz, and Provided to the adding loop block as the mixing input frequency. In the coarse tuning loop, the DAC is used to pre-tune the VCO to assist the loop locking. The specific implementation method is to add the output voltage of the low-pass loop filter through the adder and act on the voltage tuning terminal of the VCO. The DAC The output voltage of the VCO is tuned to make it oscillate near the required output frequency, so that the phase-locked loop can capture and lock. Phase detectors, mixer devices and DAC chips with low phase noise are used to further offset the phase noise performance of the system.

5) The fine-tuning loop is mainly composed of a fractional frequency division phase-locked loop and an output frequency divider. The 100MHz signal provided by the reference loop is divided by two by the reference frequency divider to generate 50MHz as the phase detection reference frequency of the fractional frequency division phase-locked loop. The fractional frequency division phase-locked loop adopts a 48-bit fractional frequency divider and a 1.5-3GHz wideband VCO To achieve this, it can output a 1.5-3GHz signal with a resolution of 1.78×10 ^-7 Hz. After the signal is divided by 12 by the output frequency divider, it can generate a low-spurious 125-250MHz signal with a resolution of 1.48×10 ^-8 Hz. output signal. The output signal of the fine-tuning loop is used as the phase detection reference signal of the adding loop, and its phase noise affects the in-band phase noise of the output signal of the adding loop module, so its output must be a signal with low phase noise and low spurious.

6) The input reference frequency of the addition loop is a high-resolution 125-250MHz frequency output by the fine-tuning loop module, and the mixing input frequency is a 3-6GHz frequency output by the coarse-tuning loop module with a step of 125MHz. Add these two groups of input frequencies to get a high-resolution 3-6GHz output frequency. The in-band output phase noise of the adding loop is mainly determined by the output phase noise of the mixing input signal, which is mainly determined by the in-band output phase noise of the coarse tuning loop, and the out-of-band output phase noise is mainly determined by the VCO.

7) The reference loop uses an OCXO with high stability and low phase noise to generate a 100MHz reference frequency. The 100MHz signal passes through a power divider, and one output is used as a reference source signal for the fine-tuning loop, and the other passes through a fixed frequency division ratio of 10. The phase-locked loop of the phase-locked loop generates a 1GHz signal. The 1GHz VCO4 of the phase-locked loop uses a high-performance VCSO. The 1GHz signal passes through a power divider, and one way is output to the DDS chip in the system as a clock signal, and the other way is generated by a two-frequency divider. 500MHz signal, the 500MHz signal passes through the power divider, one output to the comb spectrum generator module, and the other one passes through the frequency divider with variable frequency division ratio, and 125MHz, 250MHz, 375MHz are extracted by the four-channel switching filter bank And the 500MHz signal is used as the input reference signal for the coarse adjustment loop.

8) The function of the comb spectrum generator module is to provide a mixed frequency input signal with low phase noise for the coarse tuning loop module. The comb spectrum generator module is mainly composed of three parts: drive amplifier, comb spectrum generator and tuned bandpass filter. The 500MHz input signal provided by the reference module is first amplified by the drive amplifier to provide a high-power excitation signal for the comb spectrum generator. The comb spectrum generator generates a large number of 500MHz harmonics, and then the 3GHz and 3.5GHz are extracted by the tuned bandpass filter. , 4GHz, 5GHz, 5.5GHz and 6GHz, these seven frequency signals are output to the coarse tuning loop module as mixing input signals. Among them, the tuned bandpass filter can also be replaced by a switch filter bank.

Description of drawings

Fig. 1 is the structural diagram of multi-ring broadband low phase noise frequency synthesizer;

Figure 2 is a detailed structure diagram of a multi-ring broadband low-phase-noise frequency synthesizer.

Detailed ways

A realization device of a multi-loop broadband low-phase noise frequency synthesizer is characterized by comprising a reference loop, a fine-tuning loop, a rough-tuning loop, an addition loop, a comb spectrum generator module and a frequency extension module.

The reference loop includes phase detector 1, low-pass loop filter 3, VCO4, frequency divider 5, programmable frequency divider 6, switch filter bank 7, frequency divider 2 and OCXO10. The coarse tuning loop includes a phase detector 11 , a low-pass loop filter 12 , an adder 15 , a DAC 16 , a VCO 17 , a mixer 14 and a low-pass filter 13 . The fine tuning loop includes phase detector 18 , low pass loop filter 19 , VCO 20 , fractional frequency divider 22 and frequency divider 21 . The summing loop includes a phase detector 23 , a low-pass loop filter 25 , an adder 26 , a DAC 27 , a VCO 28 , a mixer 29 and a low-pass filter 24 . The comb spectrum generator module includes a comb spectrum generator 8 and an adjustable bandpass filter 9 . The frequency extension module includes frequency multiplication and frequency division switch filter bank module 30 and DDS31.

The reference loop synthesizes a high-stability, low-phase-noise reference signal for other modules as a reference signal. The 100MHz reference signal output by it is provided to the fine-tuning loop module, 1GHz is provided to the DDS of the frequency extension module, and the 500MHz reference signal is provided to the comb The spectrum generator module, 125MHz, 250MHz, 375MHz and 500MHz reference signals are provided to the coarse tuning loop module. Then, the comb spectrum generator module generates a large number of harmonic components of the 500MHz reference signal, and uses a tuned bandpass filter to extract seven frequency points (3GHz, 3.5GHz, 4GHz, 4.5GHz, 5GHz, 5.5 GHz, 6GHz) as the mixing input signal of the coarse tuning loop module, the coarse tuning loop module adds the reference frequency provided by the reference module and the output frequency of the comb spectrum generator module to generate 3-6GHz with a frequency step of 125MHz The output frequency is used as the mixing input signal of the adding loop module, and the fine tuning loop module outputs a high frequency resolution 125-250MHz signal as the reference signal of the adding loop module, and the adding loop module outputs the frequency of the coarse tuning loop module and the fine tuning loop module The output frequencies of the modules are added to generate a high-resolution 3-6GHz signal, and finally, a 0.001-18GHz signal is generated through the frequency expansion module.

Claims (3)

1. a kind of multi-loop broadband low phase noise frequency synthesizer, it is characterized in that, described frequency synthesizer comprises: reference loop, fine tuning loop, coarse tuning loop, addition loop, comb spectrum generator module and Frequency extension module; Wherein, the function of described comb spectrum generator module is to provide the mixed frequency input signal of low phase noise for rough tuning loop; Comb spectrum generator module is made up of driving amplifier, comb spectrum generator and tuning band The pass filter is composed of three parts; the 500MHz input signal provided by the reference loop is first amplified by the drive amplifier to provide a high-power excitation signal for the comb spectrum generator. The comb spectrum generator generates a large number of 500MHz harmonics, and then the tuned bandpass The filter extracts the seven frequency signals of 3GHz, 3.5GHz, 4GHz, 4.5GHz, 5GHz, 5.5GHz and 6GHz, and outputs them to the coarse tuning loop as a mixing input signal; where: The coarse tuning loop includes a phase detector (11), a low-pass loop filter (12), an adder (15), a DAC (16), a VCO (17), a mixer (14) and a low-pass filter device (13); the coarse tuning loop adopts a frequency mixing phase-locked loop structure, and its input reference frequency is these four frequency points of 125MHz, 250MHz, 375MHz and 500MHz generated by the reference loop, and the mixing input frequency is determined by the comb spectrum For the seven frequency points of 3GHz, 3.5GHz, 4GHz, 4.5GHz, 5GHz, 5.5GHz and 6GHz generated by the generator module, the coarse tuning loop adds these two sets of input frequencies to obtain 3~ 6GHz output frequency, which is provided to the adding loop as the mixing input frequency; in the rough tuning loop, the DAC (16) is used to pre-tune the VCO (17) to assist loop locking, and the specific implementation method is through the adder (15) is added with the output voltage of low-pass loop filter (12), acts on the voltage tuning terminal of VCO (17), and the output voltage tuning VCO (17) of DAC (16) makes it oscillate in required Near the output frequency, the phase-locked loop can be captured and locked; the noise performance of the coarse adjustment loop determines the phase noise performance of the system output, and a phase detector and mixer with low phase noise are used, and a low-noise voltage regulator chip is used to provide Power supply voltage, and adopts low-noise DAC chip; Described fine-tuning loop comprises phase detector (18), low-pass loop filter (19), VCO (20), fractional frequency divider (22) and frequency divider (21); The function of fine-tuning loop It provides a high-resolution phase detection reference frequency for the addition loop; the 100MHz signal provided by the reference loop is divided by the reference frequency divider to generate 50MHz as the phase detection reference frequency of the fractional frequency phase-locked loop, and the fractional frequency lock The phase loop is implemented by a 48-bit fractional frequency divider and a 1.5-3GHz wideband VCO, which can output a 1.5-3GHz signal with a resolution of 1.78×10 ^-7 Hz. After the signal is divided by 12 by the output frequency divider, a resolution 1.48×10 ^-8 Hz low spurious output signal of 125 ~ 250MHz, the output signal of the fine adjustment loop is used as the phase detection reference signal of the addition loop, and its phase noise affects the in-band of the output signal of the addition loop phase noise; The adding loop comprises a phase detector (23), a low-pass loop filter (25), an adder (26), a DAC (27), a VCO (28), a mixer (29) and a low-pass filter (24); Its input reference frequency of the addition loop is the high-resolution 125～250MHz frequency that the fine-tuning loop outputs, and the frequency mixing input frequency is the 3～6GHz frequency that takes 125MHz as the step by the rough-tuning loop output, The addition loop adds these two sets of input frequencies to obtain a high-resolution 3-6GHz output frequency; the in-band output phase noise of the addition loop is mainly determined by the output phase noise of the mixed frequency input signal, and the in-band output of the entire loop The phase noise is determined by the coarse adjustment loop, and the out-of-band output phase noise is mainly determined by the VCO of the addition loop; The reference loop includes a phase detector (1), a low-pass loop filter (3), a VCO (4), a frequency divider (5), a programmable frequency divider (6), a switch filter bank (7 ), frequency divider (2) and OCXO (10); the reference loop uses a high stability, low phase noise constant temperature crystal oscillator OCXO (10) to generate a 100MHz reference frequency, and the 100MHz signal passes through the power divider and outputs all the way The fine-tuning loop is used as a reference source signal, and the other channel generates a 1GHz signal through a phase-locked loop with a fixed frequency division ratio of 10. The 1GHz VCO (4) of the phase-locked loop uses a high-performance voltage-controlled surface acoustic wave oscillation VCSO, the 1GHz signal passes through the power divider, one way is output to the DDS chip in the system as a clock signal, the other way passes through the two frequency divider to generate a 500MHz signal, the 500MHz signal passes through the power divider, and one way is output to the comb spectrum generator module for use , and the other channel passes through a programmable frequency divider (6) with a variable frequency division ratio, and extracts 125MHz, The 250MHz, 375MHz and 500MHz signals are used as input reference signals for the coarse tuning loop; among them, 125MHz is obtained by dividing the frequency of 500MHz by four, 250MHz is obtained by dividing the frequency of 500MHz by two, and 375MHz is obtained by dividing the frequency of 500MHz by four and taking three times of 125MHz Harmonics get. 2. A kind of multi-loop broadband low-phase noise frequency synthesizer according to claim 1, characterized in that, the main body adopts a multi-loop frequency synthesis structure of frequency mixing phase-locked loop, and the output frequency range is 0.001～18GHz; the multi-loop structure The output range of the frequency synthesizer is determined by the addition loop, the output frequency range of the addition loop is 3-6GHz, and then the frequency range is extended to 0.375-18GHz through the frequency multiplier and frequency divider, and the low frequency part is synthesized by direct digital frequency Realized by DDS, the output frequency range is 0.001-0.375GHz, and finally, the output frequency range is 0.001-18GHz. 3. a kind of multi-loop broadband low-phase noise frequency synthesizer according to claim 1, is characterized in that, the output frequency resolution of multi-loop structure is equal to the output frequency resolution of fine-tuning loop, and fine-tuning loop adopts decimal Frequency-division phase-locked loop, the phase detection frequency is 50MHz, and a 48-bit fractional frequency divider is used, so the output frequency resolution of the fractional frequency-division phase-locked loop is 1.78×10 ^-7 Hz. After passing through the frequency divider with a frequency division ratio of 12, The resolution reaches 1.48×10 ^-8 Hz. After frequency multiplication and frequency division by the frequency expansion module, the frequency resolution can still reach 0.0001 Hz within the output frequency range.