RU184346U1 - FREQUENCY SYNTHESIZER - Google Patents

Abstract

The invention relates to the field of measurement technology, radar and communications. The main technical result is to reduce the step of tuning in frequency, level of phase noise and side spectral components with a uniform tuning of the output frequency over a wide range. The frequency synthesizer consists of identical serially connected synthesizer node and H additional synthesizer nodes, which are interconnected through the first input of the mixer. The input of the synthesizer node is the input of the device and is connected to the source of the reference frequencies through the first input of the mixer. The synthesizer assembly contains a mixer, the first and second frequency dividers, a frequency-phase detector, a low-pass filter, a controlled oscillator, and the first and second frequency multipliers. In the device, a first frequency divider, a frequency-phase detector, a low-pass filter, a controlled oscillator, a mixer through its second input, a second frequency divider, and a second frequency multiplier connected to another input of the frequency-phase detector are connected in series. The output of the controlled oscillator is connected to the input of the first frequency divider and to the input of the first frequency multiplier, the output of which is the output of the synthesizer node and connected to the input of the mixer of a serially connected additional synthesizer node.

Description

The invention relates to the field of measurement technology, radar and communications.

Prior art

Known frequency synthesizers, made in the form of an integrated circuit, including a frequency-phase detector, frequency dividers and a voltage controlled oscillator (https://datasheets.maximintegrated.com/en/ds/MAX2871.pdf, www.ti.com/lit/ ds / symlink / lmx2594.pdf) implementing ultra-wideband frequency synthesis with minimum dimensions and power consumption.

The main disadvantage of the known device is that it is not possible to improve the quality of the output signal spectrum by converting its frequency into feedback, since the feedback channel is physically inaccessible for connection.

Known frequency synthesizer (Patent RU No. 2523188, IPC H03L 7/16, publ. 07/20/2014), which consists of a reference oscillator, frequency multipliers, frequency dividers, frequency-phase detector, frequency converter, error signal filter and controlled oscillator . To reduce the influence of the frequency-phase detector on the quality of the spectrum of the output signal of the device, frequency conversion is used on the signal converter of the controlled oscillator in the feedback. To obtain a small frequency tuning step, a divider with variable fractional division factor and a sigma-delta modulator are used. The use of a frequency divider with a fractional division factor, a sigma-delta modulator and a frequency-phase detector in the form of a single integrated circuit allows you to save on power consumption and device dimensions.

The main disadvantage of the known device is the relative narrowband, due to the limitation of the frequency range at the input of the frequency-phase detector - almost no more than 10% of the center frequency of the range. Also, the frequency synthesizer is sensitive to the character of the spectral composition of the additional signal - the level of harmonics and subharmonics.

Known frequency synthesizer (AV Gorevoy. Low-power sources of continuous microwave signals for measuring equipment: abstract of thesis ... Ph.D., TUSUR, Tomsk, 2017, p. 11), we have chosen for the prototype, which consists of a divider frequency, frequency-phase detector, low-pass filter, controlled oscillator and mixer, in which to reduce the influence of frequency-phase detector on the quality of the spectrum of the output signal using frequency conversion on the mixer signal controlled oscillator in the feedback. An additional signal comes from the outside, and the reference frequency signal is generated by a divider of the output frequency signal with a variable integer division factor. The device is tolerant to the nature of the spectral composition of the additional signal, including allows you to work with the signal in the form of a comb of harmonics with the same levels. In this case, the device can capture the frequency in the vicinity of the selected harmonic after presetting the frequency of the controlled oscillator.

A disadvantage of the known technical solution is a rather large frequency tuning step due to the use of a frequency divider with a variable integer division ratio and a relatively small frequency tuning range. If the additional signal is a comb of harmonics, the frequency tuning range expands approximately to the comb frequency band, but there is no possibility of capturing the frequency in the vicinity of frequencies that are multiple of half the comb step.

The essence of the utility model

The main technical result achieved using the inventive utility model is to reduce the frequency tuning step, the level of phase noise and side spectral components with a uniform tuning of the output frequency over a wide range.

The main technical result is achieved by the fact that in the frequency synthesizer, which includes a synthesizer node that contains a mixer, the first input of which serves to supply a reference signal, connected in series the first frequency divider, frequency-phase detector, low-pass filter, controlled oscillator, the output of which is connected with the second input of the mixer and with the input of the first frequency divider, according to the proposed solution, H series-connected additional synthesizer nodes, identical to synthesizing, are entered A node in which the output of the controlled oscillator is connected to the input of the first frequency multiplier, and the output of the mixer is connected to the second frequency divider, the output of which is connected to the second frequency multiplier, the output of which is connected to another input of the frequency-phase detector, while the output of the first frequency multiplier is connected to the first input of the mixer of a sequentially connected additional synthesizer node, and the first frequency divider is made with a variable fractional division factor and a sigma-delta modulator.

The figure shows a functional block diagram of the inventive frequency synthesizer implemented using integrated circuits of ultra-wideband frequency synthesis with a PLL, the input of which is connected to a source of reference frequencies 1.

The frequency synthesizer consists of serially connected synthesizer node 2 and H of additional synthesizer nodes 3, which are interconnected through the first input of mixer 4. The input of synthesizer node 2 is the device input and connected to the reference frequency source 1 through the first input of mixer 4. Synthesizer node 2 contains mixer 4, first and second frequency dividers 5 and 6, frequency-phase detector 7, low pass filter 8, controlled oscillator 9, first and second frequency multipliers 10 and 11. The device is connected in series first frequency divider 5, frequency-phase detector 7, low-pass filter 8, controlled oscillator 9, mixer 4 through its second input, second frequency divider 6, second frequency multiplier 11 connected to another input of frequency-phase detector 7. Output of controlled oscillator 9 is connected to the input of the first frequency divider 5 and to the input of the first frequency multiplier 10, the output of which is the output of the synthesizer node 2 and is connected to the input of the mixer 4 of a series-connected additional synthesizer node 3.

The first and second frequency dividers 5 and 6, the frequency-phase detector 7, the controlled oscillator 9 and the second frequency multiplier 11 are made in the form of a single integrated PLL 12.

Implementation of the utility model

From the source of the reference frequency 1 to the input of the synthesizer node 2 through the first input of the mixer 4 receives the signal of the reference frequency. The output signal from the first frequency divider 5 is fed to the input of the frequency-phase detector 7. The second input of the mixer 4 receives the signal of the controlled oscillator 9. From the output of the mixer 4, a differential frequency signal equal to the frequency difference of the controlled oscillator 9 and the nearest harmonic component of the reference frequency signal is received, and is fed to the input of the second frequency divider 6 with a variable division factor R, from the output of which is fed to the second frequency multiplier 11 with a variable multiplication factor P, the output signal of which stumbles to the other input of frequency-phase detector 7. The phase-frequency detector 7 generates an error signal proportional to the phase mismatch between the signals at its inputs. This signal, after being filtered by the low-pass filter 8, is fed to the frequency control input of the controlled oscillator 9. Frequency capture in the vicinity of some harmonic component of the reference frequency signal is carried out after presetting the frequency of the controlled oscillator 9 into this neighborhood.

The output frequency of the claimed device is determined by:

Where

F _add is the frequency of one of the harmonic components of the reference frequency signal U _add (t);

M - the total number of synthesizer nodes;

L _k - the multiplication factor of the first frequency multiplier 10 synthesizer node with the number k;

N _k - division ratio of the first frequency divider 5 of the synthesizer node with the number k;

R _k / P _k is the ratio of the division ratio R _{k of the} second frequency divider 6 to the multiplication factor P _{k of the} second frequency multiplier 11 of the synthesizer node with the number k;

Where

A _i is the amplitude of the harmonic component with the number i in the spectrum of the reference frequency signal U _add (t);

ω _i is the circular frequency of the harmonic component with the number i in the spectrum of the signal of the reference frequency U _add (t).

The frequency tuning step in the inventive device:

F _{add max} is the maximum frequency in the spectrum of the harmonic components of the reference frequency signal U _add (t);

MOD _max - the highest denominator of the fractional part of the division ratio of the first frequency divider 5 in the synthesizer nodes;

INT _min - the minimum integer part of the division ratio of the first frequency divider 5 of the synthesizer node with MOD _max ;

L _kmax is the maximum multiplication factor of the first multiplier of the frequency 10 of the synthesizer node with the number k;

N _kmin - the minimum division ratio of the first frequency divider 5 of the synthesizer node with the number k;

R _k / P _kmax is the maximum ratio of the division ratio R _{k of the} second frequency divider 6 to the multiplication factor P _{kmax of the} second frequency multiplier 11 of the synthesizer node with the number k;

If the spectrum of the reference frequency signal U _add (t) is dominated by one harmonic component, the frequency tuning of synthesizer node 2 will be carried out within relatively small limits.

If several harmonic components prevail in the spectrum of the reference frequency signal U _add (t), then the frequency tuning range of synthesizer node 2 will be approximately equal to the frequency interval between the highest and lowest components and may exceed an octave. The operation of the device at H = 0 in the vicinity of the frequencies of these components and the middle between them is impossible.

При этом качество спектра выходного сигнала F_out заявляемого устройства остается характерно высоким.Each subsequent additional synthesizer node 3 scales the frequency range and the tuning step in frequency δF of the previous one with the corresponding coefficient

The quality of the spectrum of the output signal F _{out of the} proposed device remains characteristically high.

If several harmonic components prevail in the spectrum of the reference frequency signal U _add (t), adding an additional synthesizer node 3 allows the frequency synthesizer to work at frequencies where it is impossible to work with one synthesizer node 2. Thus, due to the use of only one additional synthesizer node 3, in the inventive device, a uniform frequency tuning can be implemented in the frequency range of the prevailing harmonic components, including, exceeding an octave.

In classical frequency synthesizers, improving the quality of the output signal spectrum F _out and reducing the frequency tuning step δF is achieved by frequency conversion on hybrid mixers with a large number of separate decoupling amplifiers and the introduction of direct digital synthesis chips with characteristic high power consumption and size.

Due to the integration of almost all elements of the proposed frequency synthesizer with a PLL into a single monolithic circuit, there is a need to connect only an external source of reference frequencies 1, a low-pass filter 8 for the generator control signal 9 and a small number of stabilization and power filtering elements, due to which the device has low power consumption and an area from units to several tens of square millimeters. The implementation of the mixer 3 is also in the integrated design along with a positive impact on the quality of the spectrum of the output signal leads to a slight increase in size and power consumption of the device.

Claims (1)

A frequency synthesizer that includes a synthesizer unit that contains a mixer, the first input of which serves to supply a reference signal, connected in series the first frequency divider, frequency-phase detector, low-pass filter, controlled oscillator, the output of which is connected to the second input of the mixer and to the input of the first frequency divider, characterized in that the H serially connected additional synthesizer nodes are introduced, identical to the synthesizer node in which the output of the controlled oscillator is connected to the first frequency multiplier, and the mixer output is connected to the second frequency divider, the output of which is connected to the second frequency multiplier, the output of which is connected to another input of the frequency-phase detector, while the output of the first frequency multiplier is connected to the first input of the mixer of a serially connected additional synthesizer node, and the first frequency divider is made with a variable fractional division factor and a sigma-delta modulator.

Images