KR101007211B1 - Wideband high frequency synthesizer for airborne - Google Patents

Abstract

PURPOSE: A broadband high frequency synthesizer for avionics is provided to remove a spurious frequency component by selectively passing a harmonic frequency band from a frequency signal. CONSTITUTION: An intermediate frequency oscillator circuit(10) outputs an intermediate frequency. A local oscillating circuit(20) outputs a fixed frequency. A band selector(30) comprises a first giro which mixes the fixed frequency by passing the source frequency band of the intermediate frequency. The band selector comprises a second giro which mixes the fixed frequency by passing the harmonic frequency band of the intermediate frequency. The band selector comprises a first switch which selectively connects the first and the second giro to the intermediate frequency oscillator circuit. The band selector comprises a second switch which selectively connects the first and the second giro to the local oscillating circuit.

Description

Wideband High Frequency Synthesizer for Airborne

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wideband high frequency frequency synthesizer for avionics, and more particularly, to a frequency synthesizer capable of wideband high frequency oscillation for use in avionics, ie, unmanned aerial vehicles and guided weapons.

Local oscillator (LO) frequencies from hundreds of MHz to several GHz are used to process signals in communication systems. The frequency used is less affected by low phase noise, temperature and noise interference, which ensures the performance of the system. In this case, the voltage controlled oscillator (VCO) can be directly controlled to generate the LO frequency, but the phase noise characteristics are not good, and the output frequency is sensitive to external changes such as temperature change and supply voltage noise. What is needed is a system to compensate for changes in the VCO. This creates a stable output frequency with reduced phase noise using a feedback system such as a phase locked loop (PLL). In recent years, RF component manufacturing technology has advanced rapidly, and RF components are surprisingly small and lightweight compared to the past, thus increasing the portability of the terminal. Due to this trend, miniaturization of PLL modules is proceeding rapidly. The frequency synthesizer consists of a phase locked loop (PLL), a phase locked or phase locked circuit, a voltage controlled oscillator (VCO) that oscillates the output frequency, and a loop filter (LF) for low pass and voltage conversion. Using the principle of phase locked loop, it is possible to select the desired output frequency.

PLL modules, which are essential for wireless communication systems, require cutting-edge core technologies.In the early days, Motorola and Matsushita, mainly foreign companies, produced and supplied them to domestic and overseas mobile phone manufacturers. It is being replaced by a small domestic component of less than cc, and it is possible to produce a multifunctional mobile phone which is more portable and convenient. According to 2003 statistics, 400 million mobile phones are produced annually worldwide, and more than 1 billion mobile devices are in operation. The method has also evolved from the analog method to the TDMA digital method and the CDMA method, and is expected to further develop a paradigm with an increase in the amount of data to be handled in the future. Among them, the PLL frequency synthesizer has developed into an important component that plays a role of carrier synthesis or separation in the overall wireless communication system.

In general, the frequency synthesizer refers to the entire feedback circuit including components such as a reference signal source, a PLL, a loop filter, and a VCO. However, the purpose is to stably maintain a signal synchronized with the reference signal. Therefore, in order to increase system performance, careful design of not only one component but the entire component is required. In particular, care must be taken when designing a frequency synthesizer as it has a significant effect on the analog circuits such as logic circuit design, adjacent noise characteristics, and lock-up time, which is a channel switching time.

Integer-N and Fractional-N methods are mainly used for PLL frequency synthesizers. Integer-N (Integer Dispensing) is based on the pulse swell method, which is advantageous for IC. The pulse swell-type PLL frequency synthesizer compares the phase difference of the signal divided by the reference signal source with the reference counter and the high frequency signal divided by the VCO in the phase comparator. The phase error signal corresponding to the phase difference is output from the charge pump circuit as a transient response signal, and is converted into a DC voltage by a loop filter to drive the VCO to generate a desired frequency. By repeating this operation by the feedback circuit, a stable signal is obtained. Fractional-N means fractional division, and the division ratio is fractional compared to the integer division, which is the conventional Integer-N system, and the synchronous frequency controls the feedback frequency (output frequency) by fractional multiple as well as integer multiple of the reference signal source. It is possible to increase the reference signal source arbitrarily, the phase noise characteristics can be improved.

On the other hand, existing high-frequency (X-Band) frequency synthesizers are used to multiply low frequencies in a single loop structure, or oscillate in a double-loop up-mixing or down-mixing method.

In this way, narrowband oscillation is possible, but due to structural limitations, broadband frequency synthesis of 2 to 4 GHz is impossible. In other words, the single-loop high frequency frequency synthesizer oscillates low frequency and uses a multiplier to oscillate high frequency (over X-Band). As the division ratio increases in proportion to the (output frequency), the phase noise characteristic is poor. The up-conversion double loop frequency synthesizer can obtain excellent phase noise characteristics in the high frequency band, but has a complex structure.

On the other hand, such an unmanned aerial vehicle or a guided weapon, such a frequency synthesizer must be provided inevitably. However, because the frequency synthesizer used in such a device requires a high degree of precision, the phase noise characteristics should be very excellent, and a wide frequency band should be provided.

As to solve the above problems,

An object of the present invention is to provide a frequency synthesizer excellent in phase noise characteristics.

It is also an object of the present invention to provide a frequency synthesizer with an increased bandwidth.

In order to achieve the above technical problem,

The frequency synthesizer according to the present invention includes an intermediate frequency oscillator circuit, a local oscillator circuit and a band selection circuit. The oscillator circuit outputs an intermediate frequency. The local oscillation circuit outputs a fixed frequency. The band selection circuit includes a first branch for mixing the fixed frequency by passing the source frequency band of the intermediate frequency, and a second branch for mixing the fixed frequency by passing the high frequency band of the intermediate frequency.

The band selection circuit further includes a first switch for selectively connecting the first branch and the second branch to an intermediate frequency oscillation circuit and a second switch for selectively connecting the first branch and the second branch to a local oscillation circuit. It can be provided.

Furthermore, the present invention may further include a control unit for controlling the first switch and the second switch to connect the intermediate frequency oscillation circuit and the local oscillation circuit to the same branch when selecting a specific band.

In addition, the first branch of the present invention includes a first mixer for upconverting the intermediate frequency and the local oscillation frequency, and the second branch includes a second mixer for upconverting the intermediate frequency and the local oscillation frequency. can do.

Further, the first branch may include a band selection filter, a power amplifier, and a spurious cancellation filter as the first branch. The first branch band selection filter passes the source frequency band from the intermediate frequency transmitted from the first switch and outputs the original frequency band to the first mixer. The power amplifier amplifies the signal output from the first mixer. A spurious cancellation filter removes spurious frequency components from the frequency signal output from the power amplifier to the first branch. In this case, the second branch may include a band select filter, a power amplifier, and a spurious cancellation filter. The second branch band selection filter passes the harmonic frequency band from the intermediate frequency transmitted from the second switch and outputs the harmonic frequency band to the second mixer. The power amplifier amplifies the signal output from the second mixer. A spurious rejection filter removes spurious frequency components output from the power amplifier to the second branch.

On the other hand, the first branch may further include a power amplifier and a band selection filter. The power amplifier amplifies the frequency components passed through the first switch and the first mixer. The band select filter selectively passes the source frequency band from the frequency signal output from the power amplifier to the first branch and removes the spurious frequency component. In this case, the second branch includes a power amplifier and a band selection filter. The power amplifier to the second branch amplifies the frequency components passed through the first switch and the second mixer. The band select filter to the second branch selectively passes the high frequency band from the frequency signal output from the power amplifier to the second branch, and removes the spurious frequency component.

From the structural features of the present invention described above,

The frequency synthesizer according to the present invention has excellent phase noise characteristics in the high frequency band as compared with the conventional frequency synthesizer, and also has the effect of widening the bandwidth of the conventional frequency synthesizer.

That is, the frequency synthesizer according to the present invention is suitable for equipment mounted on a seeker, an unmanned aerial vehicle or a radar of an induced weapon requiring excellent phase noise characteristics and a wide bandwidth.

1 is a block diagram schematically showing a frequency synthesizer according to the present invention.
2 is a block diagram illustrating an intermediate frequency oscillation circuit according to an exemplary embodiment of the present invention.
3 is a block diagram showing a local oscillation circuit according to an embodiment of the present invention.
4 is a block diagram showing a band selection circuit according to an embodiment of the present invention.
5 is a block diagram illustrating a band selection circuit according to another embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Throughout each embodiment, the same reference numerals refer to members performing the same functions and actions.

The frequency synthesizer according to the present embodiment can be roughly divided into the intermediate frequency oscillator circuit 10, the local oscillator circuit 20, and the band select circuit 30. Hereinafter, each circuit will be described in detail.

≪ Example 1 >

First, the intermediate frequency oscillation circuit 10 will be described with reference to FIG. 2.

The intermediate frequency oscillator circuit is configured to output an intermediate frequency and is divided into a voltage controlled oscillator (VCO) and a high frequency phase locked loop (PLL 1).

A frequency synthesizer using the phase locked loop PLL 1 divides a high frequency signal input from an external voltage controlled oscillator VCO 1 according to a predetermined division ratio. The divided signal is used as an input of a phase frequency detector (PFD) that forms a high frequency phase locked loop together with the reference signal source REF. That is, the phase locked loop PLL 1 is a negative feedback circuit that fixes the frequency in such a manner as to continuously cycle until the transmitted signal coincides with the reference signal source. Make sure you get the correct anchor point.

The intermediate frequency output from the voltage controlled oscillator VCO 1 is partially returned to the phase locked loop PLL 1 for fixing the phase through the divider DIVIDER, and partly transferred to the first switch 1 to be described later. do.

The local oscillation circuit 20 will be described with reference to FIG. 3.

The local oscillation circuit is basically the same as the above-described intermediate frequency oscillation circuit, but the frequency division ratio is fixed to output a fixed frequency. Even in the local oscillation circuit, the fixed frequency generated from the voltage controlled oscillator (VCO 2) is partially returned to the phase locked loop (PLL 2) for fixing the phase, in part through the frequency divider (DIVIDER 2), and some will be described later. It is transmitted to the second switch SWITCH 2.

The band selection circuit 30 will be described with reference to FIG. 4.

The band selection circuit includes a first switch SWITCH 1, a second switch SWITCH 2, a first branch 31, and a second branch 32.

The first switch SWITCH 1 receives the intermediate frequency and selectively connects the mixers MIXER 1 and 2 provided in the first branch 31 or the second branch 32 to be described later. In the same manner, the second switch SWITCH 2 receives a fixed frequency and selectively connects the mixers MIXER 1 and 2 provided in the first branch 31 or the second branch 32 to be described later.

The first branch 31 is configured to mix the fixed frequency by passing the source frequency band of the intermediate frequency, and in the order of processing, the first band select filter FILTER 31, the mixer MIXER 1, the amplifier AMP 3, and the like. And a second band selection filter (FILTER 32).

The first band selection filter FILTER 31 performs a function of passing only a channel band, that is, a fundamental frequency, in addition to a basic function of removing unnecessary frequency output components.

The mixer (MIXER 3) receives the passed source frequency to the IF stage and the fixed frequency to the LO stage and mixes the up conversion (Up-Mixing) method.

The amplifier AMP 31 functions to amplify the power so that a signal with sufficient power can be output at the final stage. In the case of the receiver, since the externally received signal is very small and contains very dirty noises, it is important to minimize the noise while minimizing the noise. This is because the power amplification is important because the electromagnetic wave can reach the desired place to be emitted.

Since the second band selection filter may show nonlinear spurious frequency components at the rear end of the nonlinear amplifier AMP 31, the second band selection filter finally performs bandpass filtering to remove only the desired frequency band to the outside. If a system shares an antenna with a receiver, a duplexer can replace this.

Meanwhile, an isolator may be provided as necessary. The isolator is configured to prevent a signal flowing back through the antenna, and fixes the direction of the signal so that the signal can be transmitted only in a specific direction.

The second branch 32 is configured in the same manner as the first branch 31, but the pass bands of the band pass filters FILTER 41 and 42 are different. That is, the bandpass filters FILTER 41 and 42 of the second branch 32 pass harmonic frequencies unlike the case of the first branch 31. In the second branch mixer (MIXER 4), the passed harmonic frequency is input to the IF stage, and the fixed frequency is input to the LO stage and mixed in an up-conversion (up-mixing) method.

On the other hand, when the bandwidth is selected, the first branch 31 or the second branch 32 must be selected so that a specific band is passed and mixed with a fixed frequency, so that the first switch SWITCH 1 and the second switch SWITCH 2 are selected. Should be driven simultaneously. That is, when the oscillation of the source frequency band is selected, the first switch SWITCH 1 and the second switch SWITCH 2 must be simultaneously called by a controller (not shown) so that respective frequencies are transmitted to the first branch. In the opposite case, two switches must be driven simultaneously in the same manner so that the respective frequencies are transmitted to the second branch.

Hereinafter, the operation according to the present embodiment will be described with reference to FIG. 1.

The intermediate frequency output from the voltage controlled oscillator VCO 1 of the intermediate frequency oscillator circuit 10 is transmitted to the first switch SWITCH 1, and is output from the voltage controlled oscillator VCO 2 of the fixed frequency oscillator circuit 20. The fixed frequency is transmitted to the second switch SWITCH 2.

When the control unit (not shown) is switched to the oscillation state in the source frequency band, the switch 1 (SWITCH 1) and the switch 2 (SWITCH 2) are each switched to be connected to the first branch. In this case, the intermediate frequency is transmitted to the band select filter (FILTER 31), and only the source frequency bandwidth is passed, followed by stabilization by mixing with a fixed frequency in the mixer (MIXER 1).

Conversely, when switched to the oscillation state in the harmonic frequency band, switch 1 (SWITCH 1) and switch 2 (SWITCH 2) are respectively switched to be connected to the second branch. In this case, the intermediate frequency is passed to the band select filter (FILTER 31) to pass only the harmonic frequency bandwidth, and then mixed with the fixed frequency in the mixer (MIXER 2) to stabilize.

<Example 2>

A band selection circuit 30a according to another embodiment will be described with reference to FIG. 5.

Compared to the band select circuit 30 of the first embodiment, the band select circuit 30a of the present embodiment is a case in which the band select function and the spurious cancellation function are implemented through one filter.

In this embodiment, no separate band selection filter is provided in front of the mixers MIXER 3 and 4 for mixing the source frequency and the fixed frequency. After the signal passing through the first switch SWITCH 1 enters the first branch or the second branch, the signal is up-mixed through the mixers MIXER 3 and 4 provided in each branch. The frequencies mixed through the mixers MIXER 3 and 4 are amplified to a size sufficient to transmit from the power amplifiers AMP 31 and 41 provided in each branch.

Basically, in the signal passing through the nonlinear element, not only the source frequency signal but also the harmonic component whose frequency is a multiple of it due to resonance. As the frequency multiplier increases, the size of each harmonic component decreases, but as described above, the power amplifiers AMP 31 and 41 can sufficiently amplify the signal to have a size suitable for transmission.

As described above, when passing through an amplifier, various spurious frequency components exist in the passed frequency components. The band select filter FILTER 32a of the first branch 31a selectively passes the source frequency band from the frequency signal output from the power amplifier AMP 31 of the first branch 31a, and simultaneously removes the spurious frequency component. do.

In addition, the band select filter FILTER 42a of the second branch 32a selectively passes harmonic frequency bands from the frequency signal output from the power amplifier AMP 41 of the second branch 32a, and simultaneously removes spurious frequency components. Done.

Although the preferred embodiments of the present invention have been described above, the technical spirit of the present invention is not limited to the above-described preferred embodiments, and various avionics broadband in a range not departing from the technical spirit of the present invention specified in the claims. It can be implemented with a high frequency frequency synthesizer.

10: intermediate frequency oscillator circuit 20: fixed frequency oscillator circuit
30, 30a: band selection circuit 31, 31a: first branch
32, 32a: to the second branch

Claims (6)

An intermediate frequency oscillator circuit for outputting an intermediate frequency;
Local oscillation circuit for outputting fixed frequency
A band selection circuit having a first branch for mixing the fixed frequency by passing the source frequency band of the intermediate frequency and a second branch for mixing the fixed frequency by passing the harmonic frequency band of the intermediate frequency;
The band selection circuit,
A first switch selectively connecting the first branch and the second branch to the intermediate frequency oscillation circuit;
And a second switch for selectively connecting the first branch and the second branch to the local oscillation circuit. delete The method of claim 1,
And a control unit for controlling the first switch and the second switch to connect the intermediate frequency oscillation circuit and the local oscillation circuit to the same branch when selecting a specific band. The method of claim 1,
The first branch includes a first mixer for up-converting the intermediate frequency and the local oscillation frequency, and the second branch includes a second mixer for up-converting the intermediate frequency and the local oscillation frequency. Electronic wideband high frequency synthesizer. The method of claim 4, wherein
In the first branch,
A band select filter for passing the source frequency band from the intermediate frequency transmitted from the first switch and outputting the first frequency band to the first mixer;
A power amplifier for amplifying the signal output from the first mixer;
A filter for removing spurious frequency components from a frequency signal output from the power amplifier to the first branch,
In the second branch,
A band select filter for passing a harmonic frequency band from the intermediate frequency transmitted from the second switch and outputting the harmonic frequency band to the second mixer;
A power amplifier for amplifying the signal output from the second mixer;
A wideband oscillation wideband high frequency frequency synthesizer capable of oscillating a broadband having a filter for removing a spurious frequency component from a frequency signal output from the power amplifier to the second branch. The method of claim 4, wherein
In the first branch,
A power amplifier for amplifying the frequency components passing through the first switch and the first mixer;
A band selection filter for selectively passing a source frequency band from a frequency signal output from the power amplifier to the first base and removing a spurious frequency component;
In the second branch,
A power amplifier for amplifying the frequency components passing through the first switch and the second mixer;
And a band selection filter for selectively passing a harmonic frequency band from a frequency signal output from the power amplifier to the second branch and removing a spurious frequency component.

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