RU2332787C1 - Superhigh frequency synthesiser - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: superhigh-frequency (SHF) synthesiser contains reference generator (RG), the first and second voltage driven generators (VDG), everyone being latched with Phase Locked Loop (PLL), and n identical channels of frequency spectrum formation, everyone containing series PLL-latched channel VDGs, signal switchboard, channel mixer and channel broadband filter.

EFFECT: improvement of noise characteristics; reduction of lateral harmonious components within output signal spectrum and reduction of tuning time.

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Description

The invention relates to radio engineering, in particular to devices for generating ultra-high frequency (microwave) oscillations, and can be used in exciters of transmitters and local oscillation receivers of radar systems.

A known frequency synthesizer containing a tunable generator (GH), first and second bandpass filters (PF), a series-connected reference generator (EG), a first frequency divider (PM), a first harmonic generator (GG), a first frequency selector (MF), the first mixer (CM); sequentially connected second PM, second GG, second MF, second SM; sequentially connected third DF, third GG, third MF, phase detector (PD), low-pass filter (LPF); wherein the second output of the first DF is connected to the input of the second DF, the second output of which is connected to the input of the third DF; the LPF output is connected to the PG input, the output of which is connected to the second input of the first SM, the output of which through the first PF is connected to the second output of the second SM, the output of which through the second PF is connected to the second input of the PD (Utkin G.M. Design of microwave transmitting devices. ., Sov. Radio, 1979, p. 192).

A disadvantage of the known frequency synthesizer is the impossibility of its implementation in the microwave range without the use of additional frequency multipliers, which will lead to a deterioration in the noise characteristics of the signal.

Closest to the invention is a frequency synthesizer comprising a reference generator (EG), a first frequency multiplier (UF), a second UF, a first harmonic generator (GG), a first band-pass filter (PF), a first mixer (SM), connected in series; sequentially included the second GG, the second PF, the second SM; serially connected frequency-phase-locked loop (PLL), the first voltage-controlled generator (VCO), a phase detector (PD), a DC amplifier (CT), a second VCO; wherein the first output of the EG is connected to the input of the first UCh, the output of which is connected to the input of the second GG; the second output of the EG is connected to the first input of the FAP block, to the second input of which the second output of the first VCO is connected; the output of the second VCO is connected to the second input of the first SM, the output of which through the first amplifier of the intermediate frequency (UPCH) is connected to the second input of the second SM, the output of which through the second amplifier is connected to the second input of the PD (Ibid, p.198.).

The reasons that impede the obtaining of the technical result indicated below when using a well-known frequency synthesizer are the high level of noise characteristics of the output signal due to the action of frequency multipliers and harmonic generators, insufficient output signal purity and a long tuning time.

The invention consists in the following. Its task is to improve noise characteristics, reduce the harmonic side components in the spectrum of the output signal of the frequency synthesizer and reduce the time of its tuning.

This is achieved by the fact that in a known frequency synthesizer containing a reference oscillator (EG), the second output of which is connected to the first frequency-phase locked loop (FAP) and the first voltage-controlled oscillator (VCO), connected in series with the second input first FAP; the second VCO, according to the invention, a second PLL unit is introduced, the input of which is connected to the second output of the EG, and the output is connected to the input of the second VCO, the second output of which is connected to the second input of the second block of the PLL, and n identical frequency grid channels, each of which contains in series included channel block FAP, channel VCO, channel signal switch (KSK), channel mixer (KSM) and channel broadband filter (KPF), and the second output of the channel VCO connected to the second input of the channel block FAP; the output of the KPF of each channel is connected to the second input of the KSM of the subsequent channel, and the output of the last KPF is the output of the device; the first EG output is connected to the input of the FAP channel blocks, the output of the first VCO is connected to the second input of the KSM of the first channel, and the output of the second VCO is connected to the second input of the KSC of each channel, the third input of which is connected to the generator of weight functions.

Causal relationships between the features of the invention and the technical result are as follows. In the synthesizer, the reference oscillator has the minimum frequency used, the rest of the generators have a frequency greater than the bandwidth of the channel PF. Therefore, in the spectrum of the output signal in the entire specified range of secondary component frequencies is not observed. Out of the range, side components are well suppressed by channel PFs. In the device, all generators are covered by FAP loops from a single reference generator. Therefore, the signals of all generators can be considered coherent in frequency and in slowly varying phase. At the same time, there are no frequencies floating in time in the spectrum of the output signal, which ensures the purity of the spectrum. The absence of generators tunable in the range of the circuit reduces the tuning time by 10 times compared with the prototype.

The drawing shows a functional diagram of a frequency synthesizer microwave range.

The microwave frequency synthesizer contains a reference oscillator (EG) 1, the second output of which is connected to the first phase-locked loop (FAP) 2 ₁ and the first voltage-controlled oscillator (VCO) 3 ₁ , the second output of which is connected to the second input of the first block FAP 2 ₁ , as well as in series with the second FAP 2 ₂ block and the second VCO 3 ₂ , the second output of which is connected to the second input of the second FAP 2 ₂ block. The first output of EG 1 is connected to the inputs of n identical channels of forming a frequency grid, each of which contains a channel block FAP 4, a channel VCO 5, a channel signal switch (KSK) 6, a channel mixer (KSM) 7 and a channel wide-band filter (KPF) 8. The second output of the channel VCO 5 is connected to the second input of the channel block FAP 4, the input of which is the input of the channel and connected to the output of the EG 1. The output of the KPF 8 of each channel is connected to the second input of the KSM 7 of the subsequent channel, and the output of the last KPF 8 _p is the output mustache roystva. The output of the first VCO 3 _{1 is} connected to the second input of KSM 7 _{1 of the} first channel, and the output of the second VCO 3 _{2 is} connected to the second input of KSK 6 of each channel. The third input of KSK 6 of each channel is connected to a generator of weight functions (not shown).

The described device can be performed according to known rules on a typical element base. In particular, a quartz generator of the GK-89TS type can be used as an EG (Catalog of Morion OJSC, St. Petersburg, 2001, p. 7). As VCOs 3, 5, generators made on resonators with surface acoustic waves (SAW generators), for example, type GK141-S-PV (ZhKGD468753006), were used; as the FAP units, RE3236 microcircuits were used (PEREGRINE SEMICONDUCTOR CORP. / http://www.peregrin-semi.com.), and HMC239S8 microcircuits (Hittite Microwave Corporation. / www.hittite.com.) as channel switches.

The described microwave frequency synthesizer operates as follows. The voltage with a frequency of 5-10 MHz from the output of the EG 1 is supplied to the first 3 ₁ , second 3 ₂ and channel VCOs 5, which are tied to the frequency of the EG 1 by the FAP system and generate voltages of a higher frequency, respectively, f ₁ , f ₂ , ... , f _kn . In order not to deteriorate the noise properties of SAW generators 3, 5, the cut-off band of the phase characteristic of the phase-locked loop is selected no more than 100 Hz. The output frequency of the synthesizer f _o is shifted to a predetermined range of the frequency grid by changing the frequency f _{1 of the} first VCO 3 ₁ .

The output frequency of the synthesizer f _o is determined by the following expression:

where f ₁ is the frequency of the first VCO 3 ₁ ;

f ₂ is the frequency of the second VCO 3 ₂ ;

n is the number of frequency grid channels;

Δf = f ₂ -f _k1 - step of the frequency grid;

Δf · k is the width of the synthesizer range;

k - code (number) of the selected frequency of the synthesizer, which is determined by the expression:

where a is the weight coefficient of the binary number k at the digits "0" or "1".

Thus, the output frequency of the synthesizer is formed depending on the weight function. In particular, with a zero value of k at the outputs of the channel switches 6, the voltage will have a frequency of only the second VCO 3 ₂ , and with a unit value of k-frequency of the corresponding channel VCOs 5. After converting these frequencies in the channel mixers 7, the output frequency of the synthesizer f _o is determined by the expression ( one).

Example.

Let f ₁ = 1000 MHz, Δf = 10 MHz, f ₂ = 1000 MHz, f _k1 = 1010 MHz, f _k2 = 1020 MHz, f _k3 = 1030 MHz, etc.

k = 0, n = 6 (63 letters).

In this case, only the second VCO 3 _{2 is} connected to the output of the synthesizer through the channel switches of the KSK 6 signals and the output frequency in accordance with expression (1) is determined as follows:

If we take k = 63, then all channel VCOs 5 will be connected to the output of the synthesizer.

Synthesizer Frequency Tuning Range:

The grid step frequency Δf in the microwave range less than 10 MHz is usually not done, because otherwise, neighboring stations will interfere with each other.

The synthesizer noise is determined by the following formula:

- отношение мощности шумов к мощности сигнала на несущей частоте.Where

- the ratio of noise power to signal power at the carrier frequency.

. Перейдя к выражению в децибелах, получим:The noise of all VCOs 3, 5 can be considered the same, because the generators are identical. Then

. Passing to the expression in decibels, we get:

, или

, or

In the case of using a six-channel frequency grid former n = 6. In this case, the deterioration of the signal-to-noise ratio γ _Σ is 101g7 = 8.45 dB. In the prototype, the deterioration of the signal-to-noise ratio γ _Σ when multiplied by 7 will be:

;

;

101gγ _Σ = 10lgγ + 20lgn;

20lg7 = 17 dB.

It can be seen that the noise characteristics of the claimed microwave frequency synthesizer in comparison with the prototype is at least 8 dB lower.

Claims (1)

A microwave frequency synthesizer comprising a reference oscillator, a first voltage-controlled oscillator (VCO) covered by a frequency-phase locked loop (PLL), the input of which is connected to the second output of the reference generator, a second VCO, characterized in that the second VCO is made covered by a PLL loop , the input of which is connected to the second output of the reference generator, and n identical channels of forming a frequency grid are introduced, each of which contains a channel VCO connected in series by a loop of the phase-locked loop , a channel signal switcher, a channel mixer, and a channel wideband filter, wherein the input of the PLL loop of each channel VCO is connected to the first output of the reference generator, the channel wideband filter output of each channel is connected to the second input of the channel mixer of the subsequent channel, and the output of the last channel wideband filter is device output; the output of the first VCO connected to the second input of the channel mixer of the first channel, the output of the second VCO connected to the second input of the channel switch signals of each channel, and the third input of each channel switch connected to the generator of weight functions.