KR100295441B1 - Dual frequency hopping method and apparatus frequency synthesizer - Google Patents

Abstract

end. FIELD OF THE INVENTION The claims of the present invention

A frequency hopping method and apparatus for a frequency synthesizer.

I. Problems to be Solved by the Invention

A dual frequency hopping method and apparatus for a frequency synthesizer is provided.

All. Technical gist of the present invention

In the frequency hopping method of a frequency synthesizer, an intermediate local oscillation frequency hopping process for cyclically leaping the intermediate local oscillation frequency by a predetermined frequency unit for a predetermined number of times as the sequential increase of the channel, and the intermediate local oscillating frequency It is characterized in that it consists of a radio local oscillation frequency hopping process in which the radio local oscillation frequency is hopped by a predetermined frequency unit every time it hops.

la. Important uses of the present invention

It is used for a transceiver of a wireless communication system.

Description

Dual frequency hopping method and apparatus of frequency synthesizer {DUAL FREQUENCY HOPPING METHOD AND APPARATUS FREQUENCY SYNTHESIZER}

The present invention relates to a frequency synthesis method and apparatus for a radio frequency unit of a mobile communication system, and more particularly, to a frequency hopping method and apparatus for hopping a frequency.

In a typical wireless communication system, when a dual phase locked loop (PLL) is incorporated in a frequency synthesizer of a radio frequency (RF) circuit, a single The PLL generates a radio local oscillation frequency and the other PLL generates an intermediate local oscillation frequency. These two frequencies are frequencies for generating a desired carrier frequency (Fc).

A typical frequency synthesizer consists of a reference oscillator, a phase detector (PD), a loop filter, a voltage control oscillator (VCO), and a programmable counter (PC). It is.

In the case of the dual PLL, the wireless local oscillation frequency mainly uses a fractional N counter, and the intermediate local oscillation frequency mainly uses an integer N counter. In the case of the constant N counter, the formula N = P × B + A (where P, B, and A are all integers, and P> A) is established and is composed of P, B, and A counters. In the case of fractional N counters, N = P × B + A + F (where P, B, A are integers, P> A, and F <1 is a fraction). In addition, an F counter is additionally configured.

In general, a frequency synthesizer with dual PLLs employs a frequency division multiple access (FDMA) scheme. Referring to the frequency allocation method per channel in the FDMA scheme, the integer N counter and the fractional N counter operate by receiving control data from the baseband unit. The integer N counter does not jump and always generates an intermediate local oscillation frequency of a constant frequency. And fractional N counters are generated differently by leaping by a certain frequency unit for each channel. For example, in the receiver of the satellite communications system ICO (Intermediate Circular Orbit), the intermediate local oscillation frequency is constant at 456.0 MHz, and the radio local oscillation frequency is increased by 25 kHz. In the case of the transmitter, 430.0 MHz intermediate local oscillation frequency is multiplied by 1/2 to be 215.0 MHz, which is applied to the mixer, and one of the (2200 + 0.025 × n) MHz local oscillation frequencies (in 25 kHz units) is another. Is applied to the mixer input of. At this time, the output of the mixer generates an ICO transmission frequency having a channel bandwidth of 25 kHz of {(2200 + 0.025 × n)-215} MHz = (1985 + 0.025 × n) MHz. Similarly, in the case of the receiver, the intermediate local oscillation frequency of 456.0 MHz is fixed, and the radio local oscillation frequency is changed in units of 25 kHz and applied to the mixer of the receiver.

When the satellite communication system frequency plan using the conventional method as described above, since the satellite communication system frequency bandwidth is 25 kHz, the radio local oscillation frequency must be used in units of 25 kHz. When the frequency plan is implemented, the comparison frequency of the phase detector of the phase synchronization loop for radio frequency is also 25 kHz. Even when using the fractional N counter with modulus 16, the maximum comparison frequency of the radio local oscillation frequency is 400 kHz (= 25 kHz x 16). This comparison frequency is an important factor in determining lock time in system design. The higher the comparison frequency, the faster the lock time. In general, satellite communication systems have 1199 channels and require 350ms of lock time. In the case of using so many channels, a faster lock time is required, and a higher comparison frequency is advantageous.

In view of this, the conventional method has a disadvantage in that it cannot be implemented when the lock time is to be faster, and there is a problem in that the comparison frequency cannot be smoothly changed to a desired frequency band by the designer. That is, since the frequency of the intermediate local oscillation frequency is fixed in the satellite communication system frequency plan, the comparison frequency of the radio local oscillation frequency is 25 kHz (mod. 16/16), 50 kHz (mod. 8/16), and 100 kHz (mod. Only extremely limited frequencies such as 4/16), 200 kHz (mod. 2/16), and 400 kHz (mod. 1/16) are possible.

In addition, the comparison frequency has a problem that affects not only the lock time but also phase noise.

Accordingly, an object of the present invention is to provide a dual frequency hopping method and apparatus for a frequency synthesizer that can widely use a channel band of a radio frequency in a radio frequency system.

In the method of the present invention for achieving the above object, in the frequency hopping method of the frequency synthesizer, the intermediate local oscillation frequency to hop the intermediate local oscillation frequency by a predetermined frequency unit cyclically for a predetermined number of times according to the sequential increase of the channel. It is characterized in that it comprises a hopping process and a radio local oscillation frequency hopping process for leaping the radio local oscillation frequency by a predetermined predetermined frequency unit whenever the intermediate local oscillation frequency is leaped by the predetermined number of times.

An apparatus of the present invention for achieving the above object is a frequency synthesizer having a baseband unit, a reference frequency generator that operates under the control of the baseband unit, and generates a predetermined reference frequency, the intermediate frequency receiving the reference frequency A local oscillation frequency is generated, and an intermediate local oscillator which leaps the intermediate local oscillation frequency by a predetermined low frequency unit cyclically for a predetermined number of times according to the sequential increase of channels, and receives the reference frequency and oscillates a radio local oscillation frequency. When the intermediate local oscillation frequency jumps the predetermined number of times according to the sequential increase of the channel, a wireless local oscillator is configured to hop the radio local oscillation frequency by a predetermined high frequency unit.

1 is a view showing a configuration of a radio frequency unit to which the present invention is applied;

2 is a view showing a detailed configuration of the frequency synthesizer of the radio frequency unit to which the present invention is applied;

Figure 3 shows a satellite communication frequency plan of the frequency synthesizer according to the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. First, in adding reference numerals to the components of each drawing, it should be noted that the same reference numerals have the same reference numerals as much as possible even if displayed on different drawings. In the following description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

FIG. 1 is a diagram illustrating a configuration of a radio frequency system to which the present invention is applied.

First, the reception path will be described. The duplexer 101 separates and outputs a radio signal transmitted and received through the antenna ANT. The low noise amplifier 103 receives a radio signal through the duplexer 101 and low noise amplifies the radio signal. The first mixer 107 receives the low noise amplified radio signal through the filter 105, receives the first local oscillation frequency from the radio local oscillator 142, mixes the radio signal, and outputs an intermediate frequency signal. The first receive bandpass filter 109 bandpass filters the intermediate frequency. In the case of satellite communication system, the output frequency is 215.1 ~ 215.0MHz, and the channel bandwidth is 25kHz. The intermediate frequency signal output from the first reception bandpass filter 109 is amplified by the first reception amplifier 110 and output to the second mixer 111. The second mixer 111 receives and mixes the amplified intermediate frequency signal and the second local oscillation frequency through the 1/2 divider 156 to output a baseband signal. The baseband signal is 13 MHz in the satellite communication system. The baseband signal is input to the in-phase / quadrature demodulator 117 through the second receive bandpass filter 113 and the second receive amplifier 115. The in-phase / quadrature demodulator 117 demodulates the baseband signal into in-phase data I and quadrature data Q and outputs the baseband signal to the baseband unit 160.

In the transmission path, the in-phase / quadrature modulator 119 receives the in-phase data I and the quadrature data Q from the baseband unit 160 and modulates them into baseband signals, and modulates the baseband signal through the second divider 157. It receives the local oscillation frequency and outputs the intermediate frequency signal. In this case, the intermediate frequency signal has a range of 215.1 ~ 215.0MHz, and has a bandwidth of 25kHz per channel. The intermediate frequency signal is amplified by the first transmission amplifier 121 and input to the third mixer 123. The third mixer 123 receives a mixture of the intermediate frequency amplified by the first transmission amplifier 121 and the first local oscillation frequency and outputs a radio signal. The frequency range of the radio signal is 1985.025 ~ 2014.975MHz, the bandwidth per channel is 25kHz. The radio signal is input to the duplexer 101 through the transmission band pass filter 125, the power amplifier 127 and the filter 129. The radio signal is separated from the radio signal received by the duplexer 101 and transmitted through the antenna ANT.

The frequency synthesizer 140 generates a wireless local oscillation frequency that is the first local oscillation frequency and outputs the first local oscillation frequency to the first mixer 107 and the third mixer 123 and generates an intermediate local oscillation frequency that is the second local oscillation frequency. The second mixer 111 outputs the second mixer 111 through the 1/2 divider 156 and outputs the in-phase / quadrature modulator 119 through the 1/2 divider 157.

The baseband unit 160 receives in-phase data I and quadrature data Q, which are input through the in-phase / quadrature demodulator 117 of the reception path, and transmits the in-phase data I and quadrature data Q to be transmitted. Output to phase / quadrature modulator 119. In particular, the baseband unit 160 outputs a 24-bit control signal for determining the local oscillation frequency of the frequency synthesizer 140 to the frequency synthesizer 140.

The frequency synthesizing unit 140 receives and divides the reference frequency generator 141, which is a VCTCXO (Voltage Controlled Temperature Compensated Crystal Oscillator) generating the predetermined reference frequency, and receives the reference frequency, and in the predetermined low frequency unit according to the sequential increase of the channel. The intermediate local oscillator 149 for leaping the local oscillation frequency and the reference frequency are input and divided, and when the intermediate local oscillation frequency leaps a predetermined number of times according to the sequential increase of the channel, the radio local oscillation frequency is hopped by a predetermined high frequency unit. Wireless local oscillator 142.

2 is a detailed view of the frequency synthesizer 140. Hereinafter, the wireless local oscillator 142 includes the 1 / R1 divider 143, the first phase detector 145, the first loop filter 146, the high frequency voltage controlled oscillator 147, and the like. And a first programmable counter 148. The first divider 143 divides the reference frequency into 1 / R1 and outputs the divided frequency. The first divider 143 is 13 in the case of a satellite communication system. The high frequency voltage controlled oscillator 147 receives the output of the first loop filter 146 and oscillates the radio local oscillation frequency in the radio frequency band. At this time, the oscillation frequency range is 2200.125 ~ 2230.0MHz when transmitting and 2385.125 ~ 2415.0MHz when receiving. The first programmable counter 148 is a fractional N counter. The first programmable counter 148 receives the oscillated frequency under the control of the baseband unit 160 and divides the oscillated frequency into 125 kHz steps. The first loop filter 146 low-pass filters the output signal of the first phase detector 145 and outputs it to the high frequency voltage controlled oscillator 147. The first phase detector 145 detects a phase difference between a signal output from the first divider 143 and a signal output from the first programmable counter 148 and outputs the phase difference to the first loop filter 146.

The intermediate local oscillator 149 includes a 1 / R2 divider 150 that is a second divider, a second phase detector 151, a second loop filter 152, an intermediate frequency voltage controlled oscillator 153, and a second programmable counter 154.

The second divider 150 divides the reference frequency into 1 / R2 and outputs the divided frequency. In the case of a satellite communication system, R2 is 260. The intermediate frequency voltage controlled oscillator 153 receives the output of the second loop filter 152 and oscillates the intermediate local oscillation frequency of the intermediate frequency band. The second programmable counter 154 receives the frequency oscillated by the intermediate frequency voltage controlled oscillator 153 and divides it in steps of 50 kHz under the control of the baseband unit 160. The second loop filter 152 low-pass filters the output signal of the second phase detector 151 and outputs it to the intermediate frequency voltage controlled oscillator 153. The second phase detector 151 detects a phase difference between a signal output from the second divider 150 and a signal output from the second programmable counter 154 and outputs the phase difference to the second loop filter 152.

As an example, the transmission channel 1 (TX Ch.1) will be described as an example. In the wireless local oscillator 142, after the 13 MHz frequency oscillates in the reference frequency generator 141, the first divider 143 to 1/13 is used. The frequency is divided into 1 MHz and applied to the first phase detector 145. On the other hand, a frequency of 2200.125 MHz is oscillated in the high frequency voltage controlled oscillator 147, and 1 / 2200.125 is divided in the first programmable counter 148, so that the frequency of 1 MHz is detected in the first phase detector. It is applied to the other input of 145. The first phase detector 145 compares the two frequencies (1 MHz) and outputs a wireless local oscillation frequency of 2200.125 MHz from the high frequency voltage controlled oscillator 147 only when there is no phase difference as the same frequency.

In the intermediate local oscillator 149, the reference frequency of 13 MHz is divided into 1/260 from the second divider 150 to 50 kHz, which is applied to the second phase detector 151, and the frequency of 430.2 MHz oscillated by the intermediate frequency voltage controlled oscillator 153. Is divided into 1/8604 at the second programmable counter 154, which is also 50 kHz, and is applied to the second phase detector 151. When there is no phase difference between the two signals in the second phase detector 151, a transmission intermediate local oscillation frequency of 430.2 MHz is output from the intermediate frequency voltage controlled oscillator 153.

In addition, in case of reception, only the frequency varies and operates as described above.

On the other hand, as a hopping method of the radio local oscillation frequency and the intermediate local oscillation frequency according to the present invention, in the case of transmission, the transmission intermediate local oscillation frequency changes according to the channel, 430.200MHz → 430.150MHz → 430.100MHz → 430.050MHz → 430.000MHz → 430.200 MHz (cyclic) ... in the 50 kHz step changes to the fifth channel, then the sixth channel to cycle to the same frequency as the first channel can be seen in Figure 3. In addition, the transmission local oscillation frequency remains unchanged until the fifth channel where the intermediate local oscillation frequency changes and remains 2200.125 MHz, and then jumps to 125 kHz steps in the sixth channel to reach 2200.250 MHz. In the frequency hopping method, the hopping method is the same in the receiving unit, but only slightly different frequency values.

The values of the wireless local oscillation frequency, the intermediate local oscillation frequency, and the step size (125 kHz and 25 kHz) of FIG. 1, FIG. 2, and FIG. 3 described above can be changed as required by the system designer. It can be higher than. In the case of the satellite communication system radio frequency circuit in the example of the above circuit, assuming that 8 modulus-fractional N counters are used, the comparison frequency of the radio local oscillation frequency can be up to 200 kHz as described above. As described above, the comparison frequency of the wireless local oscillation frequency may be up to 1 MHz.

As described above, the present invention has the advantage of providing a fast lock time by leaping both the intermediate local oscillation frequency and the radio local oscillation frequency in a radio frequency system.

In addition, the phase detector of the wireless local oscillator provides a variety of selection of the comparison frequency than the conventional method, thereby making it possible to select the most suitable comparison frequency for the system, thereby making the frequency plan more efficient.

Claims (4)

In the frequency hopping method of the frequency synthesizer, An intermediate local oscillation frequency hopping process in which the intermediate local oscillation frequency is cyclically hopped by a predetermined frequency unit for a predetermined number of times according to the sequential increase of the channel; And whenever the intermediate local oscillation frequency is leaped by the predetermined number of times, the wireless local oscillation frequency is hopped by a predetermined frequency unit. In the frequency synthesizer having a baseband unit and a reference frequency generator that operates under the control of the baseband unit, and generates a predetermined reference frequency, An intermediate local oscillation frequency receiving the reference frequency and generating an intermediate local oscillation frequency, the intermediate local oscillation frequency cyclically leaping the intermediate local oscillation frequency for a predetermined number of times according to a sequential increase of channels; A radio station that receives the reference frequency and oscillates a radio local oscillation frequency, and hops the radio local oscillation frequency by a predetermined high frequency unit whenever the intermediate local oscillation frequency jumps the predetermined number of times with the sequential increase of the channel. Dual frequency hopping device of the frequency synthesizer, characterized in that consisting of an oscillator. The method of claim 2, wherein the intermediate local oscillator, A divider for dividing and outputting the reference frequency at a predetermined division ratio; An intermediate frequency voltage controlled oscillator oscillating the intermediate local oscillation frequency; A programmable counter that receives the oscillated frequency and divides and outputs the oscillated frequency under the control of the baseband unit; A loop filter for low pass filtering the input signal and outputting the filtered signal to the intermediate frequency voltage controlled oscillator; Dual frequency of the frequency synthesizer characterized in that the phase detector for detecting the phase difference between the signal output from the frequency divider and the signal output from the programmable counter and outputs the phase frequency control oscillator through the loop filter. Hopping device. The wireless local oscillator of claim 2, A divider for dividing and outputting the reference frequency at a predetermined division ratio; A high frequency voltage controlled oscillator oscillating the wireless local oscillation frequency; A programmable counter for receiving the divided frequency and outputting the divided frequency; A loop filter for low pass filtering an input signal and outputting the high frequency voltage controlled oscillator; And a phase detector for detecting a phase difference between a signal output from the frequency divider and a signal output from the programmable counter and outputting the phase detector to the loop filter.