RU225423U1 - HYBRID FREQUENCY SYNTHESIZER BASED ON A FAST DIGITAL TO ANALOG CONVERTER WITH HIGH CHANGE SPEED - Google Patents

Abstract

The utility model relates to radio engineering and can be used in radio transmitting and receiving devices, as well as in control and measuring equipment. The technical result is to increase the frequency tuning speed of a hybrid frequency synthesizer based on a high-speed digital-to-analog converter. This result is achieved through the use of a hybrid frequency synthesizer in the structure based on a high-speed digital-to-analog converter of a charge pumping system, an additional charge pumping system, a controlled switch, as well as through a resistor with resistance R2, a controlled switch, a resistor with resistance R1, a capacitor with capacitance C1, a capacitor with capacitance C2, a resistor with resistance R3 and a capacitor with capacitance C3. 1 ill.

Description

Field of technology

The utility model relates to radio engineering and can be used in radio transmitting and receiving devices, as well as in control and measuring equipment.

State of the art

A hybrid frequency synthesizer based on a high-speed digital-to-analog converter in special operating modes is known from the existing level of technology [1]. This device is closest to the stated technical solution. The hybrid synthesizer is based on a PLL system, which contains a reference frequency oscillator with two outputs, a frequency-phase detector, a low-pass loop filter, a voltage-controlled oscillator, a directional coupler, a mixer in the feedback circuit, a frequency divider, a frequency multiplier, a code converter, high-speed digital-to-analog converter, bandpass filter.

The hybrid frequency synthesizer works as follows. The reference frequency generator produces a signal with a highly stable frequency, which is fed to both of its outputs. This signal via the first output is fed to one of the inputs of the frequency-phase detector, the output signal of which, through a low-pass loop filter, is fed to a voltage-controlled generator, the output frequency of which is the output frequency of the entire device, and also through a directional coupler is fed to the mixer. A signal with a highly stable frequency of the reference frequency generator is fed through the second output to a frequency multiplier, where it is multiplied n1 times, and then fed to a code converter and a high-speed digital-to-analog converter, which are interconnected by a data bus. As a result, a signal containing images of the fundamental frequency with increased amplitudes is generated at the output of a high-speed digital-to-analog converter. The image with the required number is isolated in a bandpass filter and fed to the second input of the mixer. Using a mixer, the output frequency of a voltage-controlled oscillator is shifted downward in frequency by the value of the fundamental frequency image. The frequency of the mixer output signal is then divided by a programmable frequency divider by N2 times and fed to the other input of the frequency-phase detector, which compares the signals at both inputs and generates an error signal, which, after filtering, adjusts the output frequency of the voltage-controlled oscillator.

The advantage of a hybrid synthesizer based on a high-speed digital-to-analog converter in special operating modes is that the use of a high-speed digital-to-analog converter allows you to significantly increase the amplitude of high-order fundamental frequency images, through the use of which you can ultimately increase the frequency of the signal supplied to the second input of the mixer, and thus Thus, to reduce the value of the division coefficient of the divider in the PLL feedback circuit, which leads to a decrease in the level of phase noise of the entire device. However, the disadvantage of the hybrid synthesizer is the relatively low frequency tuning speed, limited by the bandwidth of the low-pass loop filter. At the same time, increasing the bandwidth of the low-pass loop filter to increase the tuning speed of a hybrid synthesizer based on a high-speed digital-to-analog converter in special operating modes causes an increase in control signal noise, which leads to an increase in unwanted discrete spectral components of the output signal.

A frequency synthesizer with an increased tuning speed is also known [2], which is based on a phase-locked loop (PLL) system containing a frequency-phase detector PFD, an additional frequency-phase detector PFD2, a charge pumping system CHARGE PUMP, an additional charge pumping system Auxillary CPUMP , low-pass loop filter Loop Filter, formed by parallel connection of resistors R1, R2, controlled by a switch and capacitors C1 and C2, voltage-controlled oscillators VCO1, VCO2, VCO3, the signal of which is fed to a multiplexer MUX, the OUT output of which is the output of the circuit, frequency divider Divide-by-N with a programmable division factor N in the feedback circuit, as well as SPECTRUM SENSOR, Timing Synchronization Unit, Divider bit settings, VCO and MUX coarse tuning bits, Fast Lock blocks, providing synchronization and control of the frequency synthesizer with increased tuning speed.

The advantage of a frequency synthesizer with an increased tuning speed is that the additional frequency-phase detector PFD2 and the additional charge pumping system Auxillary CPUMP, coupled with the ability to connect resistor R2 in parallel with resistor R1 using a controlled switch, allow, at the time of frequency tuning, to increase the total output current of charge pumping systems in n-times, while simultaneously reducing the total resistance of parallel-connected resistors R1 and R2 in -times, due to which the bandwidth of the low-pass loop filter is expanded and the synthesizer is tuned to the desired frequency at an increased speed. After frequency tuning, the total current of the charge pump systems and the total resistance of the low-pass loop filter return to their original values, due to which the passband of the low-pass loop filter is reduced to the original values. A frequency synthesizer with an increased tuning speed has disadvantages: a significant level of phase noise due to the divider in the feedback circuit, as well as relatively large jumps in the frequency of the output signal at the time of tuning and weak suppression of control signal noise due to the low order of the low-pass loop filter.

Disclosure of the essence of the utility model

The problem to be solved by the claimed technical solution is to increase the frequency tuning speed of a hybrid frequency synthesizer based on a high-speed digital-to-analog converter.

This problem is solved by using in the structure of a hybrid frequency synthesizer based on a high-speed digital-to-analog converter of a charge pumping system, an additional charge pumping system, a controlled switch, and also by adding a resistor with resistance R2, a controlled switch, and a resistor with resistance R1 instead of a low-pass loop filter , a capacitor with capacitance C1, a capacitor with capacitance C2, a resistor with resistance R3, a capacitor with capacitance C3.

The technical result provided by this set of features is to increase the frequency tuning speed of a hybrid synthesizer based on a high-speed digital-to-analog converter.

Brief description of the figures

The essence of the claimed technical solution is illustrated in Fig. 1, which shows a block diagram of a hybrid frequency synthesizer based on a high-speed digital-to-analog converter with a high tuning speed.

A hybrid frequency synthesizer based on a high-speed digital-to-analog converter with a high tuning speed contains a reference frequency generator 1 with two outputs, the first of which is connected to one of the inputs of the frequency-phase detector 2 with two outputs, which are connected to two inputs of the charge pump system 3, connected to current bus Icontrol, and to two inputs of an additional charge pumping system 4, also connected through a controlled switch 5 to the current bus Icontrol, to which resistor 8 with resistance R2 and, through controlled switch 6, resistor 7 with resistance R1 are connected, the outputs of which are connected and connected to capacitor 9 with capacitance C1, the output of which is connected to a common bus; a capacitor 10 with capacitance C2 is also connected to the current bus Icontrol, the output of which is connected to the common bus, and a resistor 11 with resistance R3, the output of which is connected to capacitor 12 with capacitance C3, the output of which is connected to the common bus; and with the input of a voltage-controlled generator 13, the output of which is the output of the entire device and is connected to one of the inputs of the mixer 14; the second output of the reference frequency generator 1 is connected through a frequency multiplier 16 to a code converter 17 and a high-speed digital-to-analog converter 18, which are interconnected by a data bus; the output of the high-speed digital-to-analog converter 18 is connected through a bandpass filter 19 to the second input of the mixer 14, the output of which is connected through a frequency divider 15 with another input of frequency-phase detector 2.

Implementation of a utility model

The device works as follows.

Let's consider the steady state. Controlled keys 5 and 6 are open. Reference frequency generator 1 produces a signal with a highly stable frequency, which is fed to both of its outputs. This signal is supplied via the first output to one of the inputs of the frequency-phase detector 2, which produces pulse signals at the Up and Dn outputs, proportional to the phase difference of the signals at its inputs. These signals are supplied to the charge pumping system 3, which generates current Icontrol. Resistor 8 with resistance R2, capacitor 9 with capacitance C1, capacitor 10 with capacitance C2, resistor 11 with resistance R3, capacitor 12 with capacitance C3 together form a 3rd order proportional-integrating filter, which filters the control signal supplied to the generator 12, controlled voltage, the output signal of which with frequency fout is the output signal of the entire device, and is also supplied to the mixer 14.

A signal with a highly stable frequency of the reference frequency generator 1 is fed through the second output to the frequency multiplier 16, where it is multiplied by n1 times, and then fed to the code converter 17 and to the high-speed digital-to-analog converter 18, which are interconnected by a data bus. As a result, a signal containing images of the fundamental frequency with increased amplitudes is generated at the output of a high-speed digital-to-analog converter. The image with the required number is selected in the bandpass filter 19 and fed to the second input of the mixer 14.

Using the mixer 14, the output frequency of the voltage-controlled generator 13 is transferred downward in frequency by the value of the fundamental frequency image. Then the frequency of the output signal of the mixer 14 is divided in a programmable frequency divider 15 by N2 times and fed to another input of the frequency-phase detector 2, which compares the signals at both inputs and generates an error signal, which, after filtering, adjusts the output frequency of the voltage-controlled generator 13.

At the moment of frequency tuning, a control signal K is supplied to the controlled keys 5, 6. The controlled keys 5, 6 are closed. An additional charge pumping system 4 is turned on, as a result, the current Icontrol increases n-fold. At the same time, in parallel with resistor 8 with resistance R2, resistor 7 with resistance R1 is connected, selected in such a way that the relation is satisfied

This is equivalent to a low-pass loop filter extending the passband. The hybrid synthesizer quickly tunes to the required frequency. Then the control signal K is turned off. Controlled keys 5, 6 are opened. The current Icontrol returns to its original state. The passband of the loop low-pass filter takes on its original value.

The use of a third-order loop filter makes it possible to reduce the jump in the frequency of the output signal during tuning and more effectively filter the noise of the control signal.

Information sources

Romashov V.V., Yakimenko K.A., Doktorov A.N., Sochneva N.A. Hybrid frequency synthesizer based on a high-speed digital-to-analog converter in special operating modes // Utility model patent No. RU214526U1. Application 05/25/2022, publ. 02.11.2022. Bull. No. 31.

Zahir Z., Banerjee G. A 0.9–5.4 GHz wideband fast settling frequency synthesizer for 5G based consumer services // Analog Integrated Circuits and Signal Processing. 2018. Vol. 97. pp. 565–577.

Claims (1)

A hybrid frequency synthesizer based on a high-speed digital-to-analog converter with a high tuning speed, containing a reference frequency generator with two outputs, the first of which is connected to one of the inputs of a frequency-phase detector with two outputs, which are connected to two inputs of a charge pump system connected to the current bus and to two inputs of an additional charge pumping system, also connected through the first controlled switch to the current bus, to which a resistor with resistance R2 is connected and through the second controlled switch a resistor with resistance R1, the outputs of which are connected and connected to a capacitor with capacitance C1, the output of which is connected with a common bus; The current bus is also connected to a capacitor with capacitance C2, the output of which is connected to the common bus, and a resistor with resistance R3, the output of which is connected to a capacitor with capacitance C3, the output of which is connected to the common bus, and to the input of a voltage-controlled generator, the output of which is output of the entire device and is connected to one of the inputs of the mixer, the second output of the reference frequency generator is connected through a frequency multiplier to the code converter and the high-speed digital-to-analog converter, which are interconnected by a data bus, the output of the high-speed digital-to-analog converter is connected through a bandpass filter to the second input of the mixer, the output of which connected through a frequency divider to another input of the frequency-phase detector, characterized in that the hybrid synthesizer additionally includes a charge pumping system, an additional charge pumping system, a first controlled switch, a resistor with resistance R2, a second controlled switch, a resistor with resistance R1, a capacitor with capacitance C1, capacitor with capacitance C2, resistor with resistance R3, capacitor with capacitance C3.