RU187248U1 - Hybrid frequency synthesizer with enhanced spectrum clarity and extended operating frequency range - Google Patents

Abstract

A hybrid frequency synthesizer with improved spectrum purity and an extended range of operating frequencies. The proposed technical solution relates to radio engineering and can be used in radio transmitting and receiving devices, as well as in instrumentation. The technical result provided by this set of features is the extension of the operating frequency range without increasing the level of spurious components of the spectrum at the output of the device. To achieve a technical result, M grooves were introduced into the device PP frequency synthesizers (MF), each of which contains the first (1.1-M.1) and second (1.2-M.2) MF, the inputs of which are combined and are inputs of the corresponding MF groups, while the outputs of the MF are connected to the corresponding inputs of the first key (6), the output of which is connected to the input of the DAC (7), in addition, the outputs of the first frequency synthesizers of each MF group are connected to the corresponding inputs of the second key (11), the output of which is connected to one input of the mixer (12), the output of which is connected to the second ChFD input (8); one output of the VCO (10) is the output of the device, and the other through a frequency divider (13) is connected to another input of the mixer (12).

Description

A hybrid frequency synthesizer with enhanced spectrum clarity and an extended operating frequency range.

The proposed technical solution relates to radio engineering and can be used in radio transmitting and receiving devices, as well as in instrumentation.

Known hybrid one-loop frequency synthesizer [1], which is based on a phase-locked loop (PLL), containing a series-connected frequency-phase detector (ChFD), a low-pass filter (LPF) and a voltage-controlled generator (VCO), the signal of which is supplied to the output of the circuit and to one of the inputs of the mixer (SM), to the other input of which a signal is output from the output of the digital computer synthesizer (DAC), the output signal of the mixer after the required frequency division is fed to the frequency-phase detector, where e is compared with the reference frequency. In addition, a digitally synthesized synthesizer is known to US No. 6198353, H03L 7/18.

The disadvantages of analogues is that a low level of phase noise at the output of the devices is provided only for frequencies determined by the maximum output frequency of the DAC. To increase the output frequency of devices, it is necessary to increase the division coefficient in the feedback loop of the PLL to obtain the cutoff frequency of the PFD comparison, which leads to an increase in phase noise at the output of the synthesizers in proportion to the division coefficient.

The closest analogue in technical essence to the proposed device is according to the patent of the Russian Federation 172814; HO3L 7/18, adopted as a prototype.

In FIG. 1 shows a structural diagram of a prototype device, which introduced the following notation:

4 - reference frequency generator (OG);

7, 17 - the first and second digital computer synthesizers (DAC);

8 - frequency phase detector (ChFD);

9 - loop low-pass filter (LPF);

10 - voltage-controlled generator (VCO);

12 - mixer (SM);

13 - programmable frequency divider (D);

14 - directional coupler (BUT);

15 - frequency multiplier (U);

16 - band-pass filter (PF).

The prototype device contains a series-connected reference frequency generator 4, the first DAC 7, ChFD 8, a low-pass filter (LPF) 9, VCO 10 and a directional coupler 14, the output of which is the output of the device, and its second output is connected to one of the inputs of the mixer 12, the output of which through a programmable frequency divider 13 is connected to the second input of the CFD 8. In addition, the second exhaust gas output 4 is connected in series through the frequency multiplier 15, the second DAC 17 and the bandpass filter 16 to the other input of the mixer 12.

The prototype device works as follows.

The frequency of the output signal of the hybrid frequency synthesizer is tuned to another frequency due to the fact that the frequencies of the output signals of digital computing synthesizers 7 and 17 are changed so as to exclude the values of the comparison frequency of the frequency-phase detector 8, close to the frequencies of harmonics and subharmonics of the fundamental frequency of the first DAC 7, which fell into the passband of the band-pass filter 16. The error signal due to the available frequency difference at the inputs of the CFD 8 is filtered by a low-pass loop filter 9 and rebuilds the VCO 10 and the desired frequency.

The disadvantage of the prototype device is the presence of spurious components of the spectrum at the output of the device when operating in an extended frequency range, because digital computing synthesizers include digital-to-analog converters, which introduce an additional error of the output signal due to the conversion of a step-by-step digital signal into a sinusoidal analog one, and there is also no possibility of expanding the working frequency range.

The objective of the proposed hybrid frequency synthesizer with increased spectrum purity and an expanded range of operating frequencies is to expand the range of operating frequencies without increasing the level of spurious components of the spectrum at the output of the device.

To solve this problem, a hybrid frequency synthesizer with an increased spectrum purity and an extended operating frequency range, containing a reference frequency generator (OG), a digital computational synthesizer (CVS), a frequency-phase detector (ChFD), a low-pass loop filter (LPF) in series and a voltage controlled oscillator (VCO), as well as a mixer and a frequency divider, according to a utility model, M groups of frequency synthesizers are introduced, each of which contains a first and second frequency synthesizer (MF), the inputs of which are the inputs of the corresponding MF groups, and the MF outputs are connected to the corresponding inputs of the first key, the output of which is connected to the input of the DAC, in addition, the outputs of the first frequency synthesizers of each MF group are connected to the corresponding inputs of the second key, the output of which is connected to one mixer input whose output is connected to the second input of the CFD; one output of the VCO is the output of the device, and the other through a frequency divider is connected to the other input of the mixer.

In FIG. 2 shows a structural diagram of the proposed device, where the following notation is introduced:

G1 - GM - from the first to M group of frequency synthesizers (MF);

1.1, 1.2 - M.1, M.2 - frequency synthesizers included in the corresponding M groups;

4 - reference frequency generator (OG);

6, 11 - the first and second keys (K);

7 - digital computer synthesizer (DAC);

8 - frequency phase detector (ChFD);

9 - loop low-pass filter (LPF);

10 - voltage-controlled generator (VCO);

12 - mixer (SM);

13 - frequency divider (D).

The proposed device contains a reference frequency generator 4, the output of which is connected to the inputs of the M groups of frequency synthesizers G1 - GM. Each group contains the first 1.1 - M.1 and the second 1.2 - M.2 frequency synthesizers, the inputs of which are combined and are the input of the corresponding midrange group. The outputs of all the midrange are connected to the corresponding inputs of the first key 6, the output of which through series-connected DACs 7, ChFD 8 and the low-pass filter 9 is connected to the input of the VCO 10, one output of which is the output of the device, and the other through a frequency divider 13 is connected to one input of the mixer 12, the output of which is connected to the second input of the ChFD 8. In this case, the outputs of the first midrange 1.1 - M.1 are connected to the corresponding inputs of the second key 11, the output of which is connected to another input of the mixer 12.

The proposed device operates as follows.

The exhaust gas generator 4 generates a highly stable reference frequency signal, which is fed to the inputs of groups G1 - GM frequency synthesizers. The output signals of the frequency synthesizers of the M groups MF 1 - MF M are fed to the corresponding inputs of the first key 6, which switches the input of the clock frequency of the DAC 7 between the outputs of the M groups of MF. Each of the midrange is tuned to its own frequency. DAC 7 generates a signal with a small step of the frequency grid, which is fed to one of the inputs of the CFD 8, from the output of which through a low-pass loop filter 9, in which the signal is filtered from the side components of the spectrum, is fed to a generator controlled by voltage 10. From another output VCO 10 signal is fed to the input of the frequency divider 13, which divides the frequency of the signal into two. The output signal of the frequency divider 13 is fed to the first input of the mixer 12, to the second input of which there is a signal from the output of the second key 11, to the inputs of which the signals of the first synthesizers from the midrange groups are fed, starting from the output of the first midrange 1.1 of the G1 group, ending with the midrange output M.1 GM groups. Moreover, the choice between switching the midrange 1.1 - midrange M.1 depends on what frequency the device should work on (which signal is fed to the input of the DAC 7). From the output of the mixer 12 to the second input of the ChFD 8 receives the differential frequency signal. In PFD 8, the signals received at the first and second inputs are compared, and an error signal is generated at the output of PFD 8, which, after filtering, adjusts the output frequency of the VCO 10.

The presence of M groups of frequency synthesizers 1.1 and 1.2 MF (MF 1) - M.1 and M.2 MF (MF M) allows you to switch the clock frequency so that side components of the spectrum get into the passband of the low-pass loop filter 9 so that the side components of the spectrum go beyond the passband of the loop filter - this provides a cleaner spectrum of the output signal of the device while expanding the range of operating frequencies.

Thus, the use of M groups consisting of two MF allows you to tune the output signal of the device to the desired frequency by switching between groups of MF filters, while the combination of frequencies generated by them minimizes the parasitic components of the signal spectrum at the output of the proposed device.

It is possible to use the Morion GK-208 generator as an exhaust gas. Frequency synthesizers can be performed, for example, on an ADF5335 chip from Analog Devices. DAC - on the AD9914 chip from Analog Devices. PFD can be implemented, for example, on an HMC439 chip from Analog Devices. As a key, for example, Peregrine Semiconductor PE42422 key, mixer - HMC7357LP5GE by Analog Devices can be used. A low-pass loop filter can be constructed according to the standard scheme of this type of filter, for example, using the OP211 operational amplifier from Texas Instruments. Programmable frequency divider can be performed on the chip HMC402 company Analog Devices. As a VCO, for example, an MAOC-009260-PKG003 generator from M / A-COM is used.

Information sources

1. US patent, Direct digital synthesis (DDS) phase locked loop (PPL) frequency synthesizer and associated methods / Nicholas Paul Shields; Harris Corporation. - No. 7250823; claimed May 25, 2005; publ. June 31, 2007, p. 8.

2. RF patent, Hybrid frequency synthesizer with improved

spectral characteristics / Romashov Vladimir Viktorovich; Romashova Lyubov Vladimirovna; Temples Konstantin Konstantinovich; Yakimenko Kirill Alexandrovich. - No. 172814; HO3L 7/18 announced on 04.24.2017; publ. 07/25/2017, p. 4, 5, 6.

Claims (1)

A hybrid frequency synthesizer with enhanced spectrum purity and an extended operating frequency range, comprising a reference frequency generator (OG), a digital computer synthesizer (CVC), a frequency-phase detector (ChFD), a low-pass loop filter (LPF) and a voltage-controlled oscillator in series (VCO), as well as a mixer and a frequency divider, characterized in that M groups of frequency synthesizers are introduced, each of which contains the first and second frequency synthesizers (MF), the inputs of which are combined and are inputs corresponding to MF groups, while the MF outputs are connected to the corresponding inputs of the first key, the output of which is connected to the input of the DAC, in addition, the outputs of the first frequency synthesizers of each MF group are connected to the corresponding inputs of the second key, the output of which is connected to one mixer input, the output of which is connected to the second entrance of the CFD; one output of the VCO is the output of the device, and the other through a frequency divider is connected to the other input of the mixer.

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