CN209327443U - A kind of frequency spectrograph zero-frequency inhibition device - Google Patents

Abstract

The utility model discloses a kind of frequency spectrograph zero-frequencies to inhibit device, including frequency mixer, the local oscillator end of the frequency mixer is connected with first resistor, the first resistor is connected with second resistance by enameled wire, the first resistor is coupled out local oscillation signal from the local oscillator end of frequency mixer, phase shift is carried out through inductance, then has second resistance to be fed into the first intermediate frequency, the local oscillation signal of the first intermediate frequency is fed into and constant amplitude reverse phase is presented in the local oscillation signal through mixer leakage.The utility model simple possible, performance indicator low in cost, improving spectrum analyzer.

Description

A kind of frequency spectrograph zero-frequency inhibition device

Technical field

The utility model relates to spectrum analyzer, especially a kind of frequency spectrograph zero-frequency inhibits device.

Background technique

With the development of science and technology, the measurement accuracy and frequency range requirement to spectrum analyzer are higher and higher, such as Fig. 1 institute Showing, modern frequency spectrograph mostly uses greatly frequency sweep superheterodyne reception scheme, when it is 0Hz that frequency spectrograph, which is arranged, to input frequency fs, local oscillator frequency Rate fL is just equal to IF frequency fI, and the fL leakage of frequency mixer can directly be amplified by intermediate-frequency filter to intermediate frequency and wave detector, It exports through detection to scanning and shows, zero-frequency will certainly be generated.And the generation of zero-frequency affects spectrum analyzer for low frequency always The power of test of signal.

The intermediate frequency that frequency spectrograph obtains radiofrequency signal after multiple frequency-conversion processing using the method for the first local oscillator of scanning Signal.When the frequency of input radio frequency signal is 0Hz, corresponding first local oscillator signal frequency is equal to the first intermediate-freuqncy signal frequency Rate.Due to being leaked etc. the local oscillation signal of the first frequency mixer, local oscillation signal can leak to the first intermediate frequency, as the last quilt of intermediate frequency Detection output, to generate zero-frequency.Zero-frequency is exactly briefly the 0Hz Frequency point place on the frequency spectrum display window of frequency spectrograph The residual response signal of display.If the residual response signal amplitude is very high, for testing the dynamic range and frequency of low frequency signal The frequency signal lower limit etc. that spectrum analysis instrument can be tested, which can generate, to be seriously affected.Therefore refer to improve the performance of spectrum analyzer Mark, needs joined zero-frequency suppression circuit to reduce zero-frequency amplitude.

Summary of the invention

Aiming at the problems existing in the prior art, the utility model provide a kind of simple possible, it is low in cost, improve frequency The frequency spectrograph zero-frequency of the performance indicator of spectrum analysis instrument inhibits device.

The purpose of this utility model is achieved through the following technical solutions.

A kind of frequency spectrograph zero-frequency inhibition device, including frequency mixer, the local oscillator end of the frequency mixer are connected with first resistor, institute It states first resistor and second resistance is connected with by enameled wire, the first resistor is coupled out local oscillator letter from the local oscillator end of frequency mixer Number, phase shift is carried out through inductance, then there is second resistance to be fed into the first intermediate frequency, is fed into the local oscillation signal of the first intermediate frequency and through being mixed Constant amplitude reverse phase is presented in the local oscillation signal of device leakage.

The resistance value of the first resistor and second resistance is 220 Ω.

The enamel-cover line length is the enameled wire of the Φ 0.6mm of 10mm.

Compared with the prior art, utility model has the advantages that for the frequency signal near zero-frequency, if zero-frequency is believed Number amplitude is very big (being greater than measured signal amplitude), as shown in Figure 2 (a), then, measured signal f1 and f2 may can be submerged in zero At the edge of distributed of the response curve of frequency signal, so that the range of dynamic measurement of measured signal becomes very little；And only exist Compare on the Frequency point far from zero-frequency, range of dynamic measurement just will increase.If zero frequency signal amplitude is very low, can by Fig. 2 (b) Know, the range of dynamic measurement of measured signal f1 and f2 significantly increase, and can measured minimum frequency signal also can be more Close to 0Hz.

Detailed description of the invention

Fig. 1 is superhet frequency spectrograph simplified pinciple figure.

Fig. 2 is zero-frequency inhibiting effect schematic diagram.

Fig. 3 is the utility model principle schematic diagram.

Fig. 4 is the utility model structure chart.

Fig. 5 is the actual effect figure that the utility model zero-frequency inhibits.

Specific embodiment

With reference to the accompanying drawings of the specification and specific embodiment, the utility model is described in detail.

As shown in figure 3, whole device includes the long enameled wire of 2 resistance and one section of 10mm or so.The resistance value of resistance all exists 220 Ω or so specifically have debugging to determine.The length and shape of enameled wire are also determined by debugging.

It is coupled out certain local oscillation signal from the local oscillator end of frequency mixer with resistance R1, carries out phase shift through inductance L, then have resistance R2 is fed into the first intermediate frequency, and adjusting resistance R1, R2 and inductance L appropriate make the local oscillation signal for being fed into the first intermediate frequency and through mixed Constant amplitude reverse phase is presented in the local oscillation signal of frequency device leakage, can thus realize to the local-oscillator leakage of frequency mixer and inhibit well, i.e., and zero Frequency inhibits.It since program circuit is simple, low in cost, realizes and debugging difficulty is little, so having good practical valence Value.

As shown in Figure 4.R222 in Fig. 4 (a) is equal to the R1 of Fig. 3, and R218 is equal to the R2 of Fig. 3, and R201 is 0 Ω electricity Resistance.Enameled wire in Fig. 4 (b) is equal to the L of Fig. 3, and U201 is the first frequency mixer of frequency spectrograph receiving channel.

According to the technical parameter of frequency mixer, the DEMO circuit of a mixing is made, signal source exports 16dBm signal through constant amplitude With Xiang Gongfen two-way, all the way as the local oscillation signal of frequency mixer, it is used as reference signal all the way.By the leakage of mixer intermediate-frequency port Signal and reference signal are connected to 2 ports arrow net.Net work is sweared in double-receiver mode, measurable leakage signal is believed relative to reference Number amplitude in phase.ADS modeling and simulating is carried out according to measured amplitude and phase information.It is calculated in 13dBm local oscillator In the case where power, R1 and R2 take 220 ohm, and L takes the enameled wire of the Φ 0.6mm of length 10mm or so.

It is in next step exactly the practical debugging efforts of complete machine after carrying out emulation.By the of the reception frequency conversion channel of frequency spectrograph One local frequency is set as the first IF frequency (corresponding to the zero-frequency of radio-frequency input signals frequency).Inhibit device in no zero-frequency In the case where, it can be appreciated that the big signal of zero-frequency such as Fig. 5 (a) on the display screen of frequency spectrograph, amplitude is far more than detection electricity The maximum input level on road causes the compression of detecting circuit, and Marker shows that zero-frequency level is+6.92dBm in figure.In addition as schemed Zero-frequency shown in 4 inhibits device, and successively carries out debugging slightly to inductance and resistance.Zero frequency signal can be made to be greatly lowered, such as Zero frequency signal power shown in Fig. 5 (b) is -6.18dBm.

Such as want to obtain better zero-frequency inhibitory effect, then needs a bit fine debugging.We are several by several batches The production verifying of hundred frequency spectrographs, zero frequency signal level easily can debug -5dBm hereinafter, some batch zero frequency signals Level can -10dBm or less.

Facts proved that it is that a kind of simple possible, low-cost zero-frequency inhibit good that this simple spectrum instrument zero-frequency, which inhibits device, Method is worthy to be popularized.

Claims (3)

1. a kind of frequency spectrograph zero-frequency inhibits device, including frequency mixer, it is characterised in that the local oscillator end of the frequency mixer is connected with the One resistance, the first resistor are connected with second resistance by enameled wire, and the first resistor is coupled from the local oscillator end of frequency mixer Local oscillation signal out carries out phase shift through inductance, then has second resistance to be fed into the first intermediate frequency, is fed into the local oscillation signal of the first intermediate frequency Constant amplitude reverse phase is presented with the local oscillation signal through mixer leakage.

2. a kind of frequency spectrograph zero-frequency according to claim 1 inhibits device, it is characterised in that the first resistor and second The resistance value of resistance is 220 Ω.

3. a kind of frequency spectrograph zero-frequency according to claim 1 or 2 inhibits device, it is characterised in that the enamel-cover line length is The enameled wire of the Φ 0.6mm of 10mm.