KR100549818B1 - A frequency convert circuit - Google Patents

Abstract

The present invention relates to a frequency conversion circuit, and more particularly, to a frequency conversion circuit using a self-oscillating mixer. The present invention provides a self-bias type FET power supply configured in a self-oscillating mixer (SOM) for designing / manufacturing a self-oscillating mixer (SOM) having excellent frequency characteristics and improving operating characteristics of twice the frequency. The voltage and current of the circuit were adjusted and the impedance of the input / output of the FET was matched. Accordingly, the present invention can operate as a local oscillator and a frequency converter using one self oscillation mixer. In the present invention, the second harmonic signal is maximized by using the nonlinear operating characteristics of the self-oscillating mixer, so that the characteristic at the double frequency can be excellently operated.

Self-oscillating mixer (SOM), satellite broadcasting, satellite communication, down-converter, local oscillator, frequency multiplier, frequency conversion circuit.

Description

A frequency convert circuit

1A to 1D are circuit boards used in a general frequency up / down converter.

Figure 2 is a conventional frequency conversion circuit used for the frequency conversion of Figures 1a to 1d.

3 is a circuit diagram of a self-oscillating mixer (SOM).

4 is an experimental configuration of a self-oscillating mixer (SOM) according to the present invention.

5 is a waveform diagram showing an intermediate frequency (IF) amplifier stage final output and an image component.

6 is an output waveform diagram of an intermediate frequency (IF) amplifier stage according to a change of a radio frequency (RF) signal.

7 is a production layout of the self-oscillating mixer (SOM).

8 is a circuit diagram showing a frequency conversion circuit including a self-oscillating mixer (SOM) according to the present invention.

        Explanation of symbols on the main parts of the drawings

1,3,12,17: bandpass filter 3,6,8,9,14: lowpass filter

2,5,7: Up / down converter 10: Power combiner

11: voltage regulator 13: active frequency converter

15: local oscillator 16: self-oscillating mixer

18: magnetic bias circuit 200: low noise amplifier (LNA)

210: Image rejection filter (IRF) 220: Self-oscillating mixer (SOM)                 

220a: mixer 220b: oscillator

230: Low pass filter (LPF) 240: Intermediate frequency amplifier (IFA)

The present invention relates to a frequency conversion circuit, and more particularly, to a frequency conversion circuit including a self-oscillating mixer capable of operating as a local oscillator and a frequency changer.

Hereinafter, a conventional local oscillator will be described.

1A to 1D are circuit boards used in a general frequency up / down converter.

In general, as a method of manufacturing a K / Ka-Band band up / down converter, an active mixer using a diode mixer or a field effect transistor (FET) is made separately, and an oscillate is used as a K, Ka-Band band. In addition, K-Ka-Band band up / down converters must be fabricated through a wide bonding process using expensive public microwave monolithic integrated circuits (MMICs).

1A to 1C illustrate a diode mixer used in an up / down converter, in which a conversion loss of about -9 dB occurs in the K, Ka-Band band, and additional components are inevitable. FIG. 1D is an active mixer used for up / down converter, but can obtain a conversion gain of 2-3 dB, but requires a separate power supply converter, and requires separate adjustment for each product.

2 is a conventional frequency conversion circuit used for the frequency conversion of FIGS. 1A to 1D.

As shown in the drawing, a conventional local oscillator includes a low noise amplifier 100, a band pass filter 110, an oscillator 130, a mixer 120, a low pass filter 140, and an intermediate frequency. It is configured to include an amplifier 150.

The low noise amplifier (LNA) 100 amplifies the input signal with minimized noise.

The bandpass filter 110 passes a signal existing in a specific range of frequencies at the receiver and removes the signal out of this range.

The oscillator 130 generates electrical vibration of the signal.

Mixer 120 obtains one output signal from two or more input signals.

The low pass filter (LPF) 140 separates an input signal and a local oscillation signal versus an intermediate frequency.

When the signal is transmitted through an antenna installed on the ground, as shown in FIG. 1, the signal is sent to the input terminal of the down-converter at a frequency (20.2 GHz to 21.2 GHz as an embodiment of the present invention). Then, the signal amplifies the signal with low noise while passing through the low noise amplifier 100 through the input stage, passes through the bandpass filter 110, filters the frequency to be used, and transfers it to the mixer 120. do.

The mixer 120 is a device for frequency conversion (up / down conversion), the reference frequency is oscillated in the local oscillator (or oscillator) (130). The local oscillator 130 uses 9.625 GHz, and when the down conversion is performed based on this signal (operation is twice frequency, that is, 19.25 GHz), the local oscillator 130 becomes 10.575 GHz to 11.575 GHz.

That is, the frequency of the downconverted signal is measured as follows.

Input Signal-Local Oscillation Frequency = Downconverted Signal Frequency

(In general, the downconverted signal frequency is the intermediate frequency (IF).)

Therefore, the application of the frequencies of the broadcast frequency (BS) and the communication frequency (CS) described above appears as follows.

20.2 GHz-19.25 GHz = 950 MHz, 21.2 GHz-19.25 GHz = 1950 MHz

The down-converted signal is filtered again through the low pass filter 140, amplified again through the intermediate frequency amplifier 150, and output to the output terminal 170. The output terminal 170 is an input such as a receiver installed indoors, and the signal sent to the receiver performs demodulation and other signal restoration operations. Accordingly, the audio and video signals can be checked through the screen of the TV connected to the receiver.

The local oscillator illustrated in FIG. 2 should generate a high frequency local oscillation frequency of the K, Ka-Band band directly using an oscillate. However, expensive fabrication is required to generate such high frequencies. Nevertheless, in the related art, it is difficult to secure frequency stability because it is sensitively converted to integer values of peripheral circuits such as negative resistance.

Therefore, mixers, active mixers, and oscillates that use diodes, which have been used in manufacturing conventional up / down converters for satellite broadcasting and satellite communication in the K, Ka-Band bands, use high frequencies, Fabrication was difficult and demanded precision. As a result, problems such as high cost and instability of the fabrication were exhibited.

Accordingly, an object of the present invention is to provide a frequency conversion circuit including a self-oscillating mixer having a high frequency characteristic by manufacturing in a low frequency band.

According to an aspect of the present invention, there is provided a frequency conversion circuit, comprising: a self-oscillating mixer configured to perform functions of a local oscillator, a mixer, and a frequency multiplier; A low noise amplifier for amplifying the input signal with minimized noise; An image rejection filter for removing the image signal; A low pass filter separating the intermediate frequency of the input signal; It consists of an intermediate frequency amplifier that amplifies the intermediate frequency.

In the frequency conversion circuit according to the present invention, the self-oscillating mixer is characterized by performing frequency multiplication by using an HEMT element.                     

The frequency conversion circuit according to the present invention is characterized by converting the up / down frequencies of the Ka band by using the Ku oscillation self-oscillating mixer.

In addition, the frequency conversion circuit according to the present invention is characterized by converting the up / down frequencies of the K band by using a self-oscillating mixer of the Ku band.

Hereinafter, the frequency conversion circuit according to the present invention will be described in detail.

In recent years, as the microwave communication system is developed, the modules applied to the front-end of the transmitter / receiver have been developed in the trend of low cost-high performance. Wireless integrated circuits (RF ICs) / microwave monolithic integrated circuits (MMICs) are also being developed that feature low cost, high performance. In case of local oscillator, high stability characteristics and low phase noise are required, and in digital communication, oscillator is required by the relationship between BER and phase noise.

In consideration of these characteristics, the oscillator designs a high-definition DRO, and the mixer is a gate mixer, applying the characteristics of a self-oscillation mixer (SOM) that combines an existing oscillator and a mixer to the front-end. In this case, in designing a transmission / reception module of a digital microwave communication system, it is possible to develop a chipset for designing a local oscillator and a mixer as one module.

The general microwave transceiver (Microwave Transceiver) is composed of the frequency converter circuit of the up / down converter. The upconverter is composed of a power amplifier (HPA), a bandpass filter (BPF), and a mixer (MIXER). The downconverter is an active element such as a gallium arsenide field effect transistor (GaAs FET) (or HEMT) and low noise of three or more stages. It consists of a mixer, a local oscillator (VCO or DRO) and an intermediate frequency (IF) amplifier stage by means of an amplifier and a diode.

Conventional diode mixers applied to low noise downconverters in a receiving system exhibit conversion losses due to diodes. In the conventional diode-type mixer, a separate local oscillator must be designed. However, in the case of the self-oscillating mixer, one active element may simultaneously form the local oscillation signal and the mixer function, and may represent the conversion gain by the active element. Therefore, there is an advantage in reducing the number of amplification stages or intermediate frequency (IF) amplifier stage of the down-changer.

In general, various frequency bands exist, and the difficulty of fabricating the downconverter is determined for each frequency band. Fabrication and workability on frequencies in the X- and Ku bands are easy enough for mass production. However, the production of products using frequencies above the X-band, the Ku band higher than the Ku band, and the Ka band higher than the K band is sensitive enough to be difficult for the manufacturer to manually tune and manufacture. Accordingly, in designing the circuit, it is more difficult to design the circuit in the K band and the Ka band than in the X-band and the Ku band where the frequency band is low.

For example, the length of the device produced in the Ku band is reduced to less than half in the K, Ka band. At this time, since the unit representing the length of the device to be produced is so small that mm is used, a difference of more than half represents a significant difference in actual size. Therefore, as the size of the device is reduced, it becomes more difficult to manufacture and design. And if manufacturing and design are difficult, manufacturing costs increase.

Accordingly, the present invention shows a frequency conversion circuit that can be easily used in the K, Ka band by producing a self-oscillating mixer (SOM) including a frequency converter and a local oscillator, such as up / down converter.

3 is a circuit diagram of a self-oscillating mixer.

The role of the self-oscillating mixer (SOM) 16 is a circuit which simultaneously shows the characteristics of frequency up / down conversion, local oscillator, and multiplier. A HEMT (High Electron Mobility Transistor) device and bias components are configured in the circuit shown in FIG. 3. When the devices are biased (voltage and current conditions), the frequency of the input signal is converted up and down based on the local oscillator. For this reason, if the impedance of the input and output terminals of the bias and the self-oscillation mixer is changed, it also serves as a frequency multiplier.

As such, the self-oscillation mixer can operate as a local oscillator and a frequency converter in a high band such as the K and Ka bands while being used in the low band. And the self-oscillation mixer changes the impedance of the input and output to operate at twice the frequency by performing the role of frequency multiplier.

4 is an experimental configuration of a self-oscillating mixer (SOM) according to the present invention, Figure 5 is a waveform diagram showing the final output and the image components of the intermediate frequency (IF) amplifier stage, Figure 6 is the intermediate according to the change in the radio (RF) signal Fig. 7 shows the layout of the frequency (IF) amplifier stage output waveform.                     

A self-oscillation mixer (SOM) is a control configuration for simultaneously performing the roles of a local oscillator, a mixer, and a frequency multiplier. As shown in FIG. 4, after a radio (RF) signal is incident, the signal passes through an interdigital band pass filter (BPF). In this way, a band pass filter (BPF) is designed so that the separation characteristics between RF-SO (Self-Oscillation) frequencies are represented by a band pass filter at the input of the self-oscillation mixer.

FIG. 5 shows an IF signal and an image signal that appear when an RF signal is applied from 18.727 GHz to 18.627 GHz. It can be seen that the difference between the intermediate frequency signal and the image signal is -32dB.

FIG. 6 shows output characteristics after passing through a self-oscillation mixer and an intermediate frequency amplifier (IF AMP) when an RF signal is applied to −50 dBm to 10 dBm. The conversion gain is 3.17dB which is calculated by considering the loss of bandpass filter, cable loss and gain of intermediate frequency (IF) amplifier.

In the present invention, the experimental value such as the frequency value and the conversion gain value may vary according to the characteristics of the experimental element used to construct the self-oscillation mixer.

8 is a circuit diagram showing a frequency conversion circuit including a self-oscillating mixer according to the present invention.

As shown in the figure, the frequency conversion circuit according to the present invention includes a low noise amplifier 200, an image rejection filter 210, a self-oscillation mixer 220, a low pass filter 230, and an intermediate It is configured to include a frequency amplifier 240.                     

The low noise filter (LNA) 200 amplifies the input signal with minimized noise.

The image rejection filter (IRF) 210 removes the image signal.

A self-oscillation mixer (SOM) simultaneously performs the role of a local oscillator 220b, a mixer 220a, and a frequency multiplier.

Local oscillator 220b is a two oscillator in a radio page receiver, which is mixed with the received frequency to create the desired primary intermediate frequency, and mixed with the primary intermediate frequency (455 kHz). Make The mixer 220a obtains one output signal from two or more input signals, and the frequency multiplier processes a multiplier several digits at once for the purpose of high speed processing.

Thus, the self-oscillating mixer 220 can operate as a local oscillator and a frequency converter in a high band such as a Ku band while using in a low band. The self-oscillating mixer 220 changes the impedance of the input / output to operate at twice the frequency by performing the role of the frequency multiplier.

The low pass filter (LPF) 230 separates the input signal and the local oscillation signal versus the intermediate frequency.

For example, an operation embodiment of the frequency conversion circuit of the present invention will be described.

If the frequency of the local oscillator is 9.626 GHz and the input frequency is 20.2 GHz-21.2 GHz, the harmonics appearing in the self-oscillating mixer of the present invention continue to appear at multiples such as 19.25 GHz and 28.875 GHz.

Then, the frequency is up / down converted to the power level of the constant local oscillator required by the mixer so as to select and obtain the highest power level among the harmonics appearing in the self-oscillation mixer 220. This is done by matching the input / output impedance and adjusting the bias (voltage and current).

That is, if a frequency twice the frequency to be used for a frequency conversion circuit including a self-oscillating mixer (SOM) optimized at twice the frequency is input, the frequency conversion circuit passing the self oscillation mixer converts the up / down frequency to a desired frequency. The desired frequency value can be obtained. As a result, the characteristics of the high frequency band can be output even in the low frequency band.

Therefore, as described above, the frequency conversion circuit according to the present invention has the following characteristics.

1) Excellent frequency multiplication characteristics.

2) The removal of high image frequencies is effective.

3) High radio frequency value can be obtained from local oscillator.

4) High conversion gain can be obtained.

5) It has low noise.

As described above, the present invention provides a frequency conversion circuit that simultaneously performs the roles of the local oscillator, the mixer, and the frequency exhaust in the high band by using the double frequency characteristics of the low-performance, high-performance self-oscillating mixer used in the low band. It is assumed that the basic technical idea.

The rights of the present invention are not limited to the embodiments described above, but are defined by the claims, and those skilled in the art can make various modifications and adaptations within the scope of the claims. It is self-evident.

Therefore, the following effects can be expected due to the frequency conversion circuit including the self-oscillating mixer according to the present invention.

The present invention includes a frequency conversion circuit including a self-oscillating mixer to facilitate the design, fabrication and control of the frequency band, local oscillator, and multiplier to facilitate frequency switching to high-band K, Ka-Band. Was constructed.

Thus, by applying the self-oscillating mixer according to the present invention, equipment that can utilize the frequencies of K, Ka-Band (satellite communication, satellite broadcasting, BWLL, LMDS (local multi- point distribution service)) can facilitate the development of services.

Claims (4)

In the frequency conversion circuit, It provides a self-oscillating mixer in which the mixer and the local oscillator are modularized to output an intermediate frequency signal. The self-oscillating mixer performs a frequency conversion function in which the frequency of the input signal is converted up / down based on the local oscillator when a bias of a predetermined condition is given, and also changes in the impedance of the input / output terminals of the bias and the self-oscillating mixer. And converting the up / down frequencies of the K band and the Ka band by a frequency multiplying function that multiplies the frequencies accordingly. The method of claim 1, And the self oscillation mixer performs frequency multiplication using a high electron mobility transistor (HEMT). delete delete

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