CN204836145U - Fast speed adjusting in broadband is receiver frequently based on DDS - Google Patents

Abstract

The utility model discloses a quick frequency hopping receiver in broadband based on DDS, including a single -pole double -throw, two preamplification wave filters, the 2nd single -pole double -throw, intermediate frequency processing passageway, adc and the main control chip that connect gradually, main control chip controls a single -pole double -throw and the 2nd single -pole double -throw respectively to connect the 3rd single -pole double -throw through variable local oscillator module, the 3rd single -pole double -throw connects in parallel at the output of individual preamplification wave filter in the 2nd single -pole double -throw. The utility model discloses based on in DDS's the quick frequency hopping receiver, adopt DDS to obtain the required high frequency local oscillator of mixing as low frequency variable frequency source, the mode of utilizing the frequency multiplier to add filtering.

Description

A kind of broadband fast frequency hopping receiver based on DDS

Technical field

The utility model relates to a kind of receiver, is particularly applicable to the fast frequency-hopped receiver in the broadband based on DDS of broadband Spectrum of Electromagnetic Radiation monitoring.

Background technology

Modern society is along with the extensive application of each electronic product, and people also more and more pay close attention to the electromagnetic radiation intensity that electronic product produces, as conventional household electrical appliances such as mobile phone, microwave oven, television set, wireless WIFI.And the wave frequency that each electronic product uses is also more and more higher, medium wave broadcast from past hundreds of KHz, the FM broadcasting to hundreds of MHz and TV, by now mobile phone, wireless WIFI etc. have all used the frequency of a few GHz, can predict centimeter wave and millimeter wave close to our life more and more.Along with the raising of living standards of the people, the level of understanding of people to the safety problem of electromagnetic environment is improved.In some public arena of more American-European developed countries, require that cellphone subscriber forbids answering in this region or dialing mobile phone, even require closing hand phone.Electromagnetic radiation is safe from harm to human body on earth, and harm has much, goes back the answer of neither one specialty about this problem at present.But, it has been generally acknowledged that high-octane electromagnetic impulse can have a negative impact to health.And from quantum angle, high-frequency signal is larger than low frequency signal harm.

It is wide that direct digital synthesiser (DDS) technology has opposite band, and frequency agility speed is fast, and frequency resolution is high, exports the features such as Phase Continuation.But its digital structure also causes it to have following shortcoming: by the impact of device, speed as DA, ROM limits, and clock frequency is generally up to 2GHz, and its output frequency generally can only reach 0.4 times of clock frequency, when its high band exports, spurious level is also relatively large.

Adopt DDS+ frequency doubling technology, utilize the effective broadband signal of spuious lower low frequency in DDS, expand its upper limiting frequency by frequency multiplication, obtain the broadband signal of high band.Frequency doubling technology has a lot of method, as step pipe frequency multiplication, multiplier frequency multiplication, transistor active frequency multiplication, phase-locked loop (PLL) frequency multiplication etc.Comparatively speaking, step pipe frequency multiplication and transistor active frequency multiplication are a kind of arrowband frequencys multiplication, need corresponding match circuit normally to work.PLL frequency multiplication is a degenerative process of loop, and Frequency Locking needs certain hour, and normally hundreds of is delicate.Multiplier frequency multiplication bandwidth of operation is wider, can octave work, but frequency multiplication number of times is lower, and frequency multiplication gain is little.Frequency multiplication number of times is generally X2 or X4.

Utility model content

The purpose of this utility model is that a kind of fast frequency-hopped receiver based on DDS of design is for wideband electromagnetic frequency spectrum Real-Time Monitoring.

The utility model discloses the fast frequency-hopped receiver in a kind of broadband based on DDS, comprise the first single-pole double-throw switch (SPDT) connected successively, two preamplifier filters, two frequency mixers, the second single-pole double-throw switch (SPDT), intermediate frequency process passage, analog to digital converter and main control chips; Main control chip controls the first single-pole double-throw switch (SPDT) and the second single-pole double-throw switch (SPDT) respectively, and by variable local oscillator model calling the 3rd single-pole double-throw switch (SPDT), the 3rd single-pole double-throw switch (SPDT) connects described two frequency mixers respectively.

In the utility model, described two preamplifier filters comprise first passage preamplifier filter and second channel preamplifier filter, respectively corresponding first frequency mixer and the second frequency mixer.

In the utility model, described variable local oscillator module comprises the direct digital synthesiser, the first hilted broadsword four throw switch, four groups of frequency multiplication filtering and amplifying circuits and the second hilted broadsword four throw switch that connect successively, wherein direct digital synthesiser receives the DDS frequency control signal that main control chip sends, and the first hilted broadsword four throw switch and the second hilted broadsword four throw switch receive the switch controlling signal that main control chip sends.

In the utility model, described frequency multiplication filtering and amplifying circuit comprises the first amplifier, multiplier frequency multiplication, the first filter, the second amplifier and the second filter that connect successively.

In the utility model, described intermediate frequency process passage comprises the first amplifilter, three-mixer, the second amplifilter and the logarithmic detector that connect successively.

The utility model is based in the fast frequency-hopped receiver of DDS, and adopt DDS as low frequency variable frequency source, the mode utilizing frequency multiplier to add filtering obtains the high-frequency local oscillation needed for mixing.Frequency-hopping receiver adopts double superheterodyne receiver mode.For suppressing the interference of image frequency, whole receiver switches to two passages by microwave switch and receives.

Variable local oscillator frequency hopping speed of the present utility model is fast, and receiver can, in 1ms interscan 4GHz bandwidth, make signal capture probability significantly promote.

It should be noted that, improvement of the present utility model is formation and the annexation of hardware, does not rely on software program and control method that any those skilled in the art need innovation.Those skilled in the art according to content disclosed in the present application, can solve the technical problem that the application proposes, reach the technique effect described in the application after seeing that the hardware of the application is formed.

Accompanying drawing explanation

Fig. 1 is frequency-hopping receiver composition schematic diagram.

Fig. 2 variable local oscillator module composition schematic diagram.

Fig. 3 is the signal of frequency multiplication amplifilter.

Embodiment

As shown in FIG. 1 to 3, the utility model discloses the fast frequency-hopped receiver in a kind of broadband based on DDS, comprise the first single-pole double-throw switch (SPDT) connected successively, two preamplifier filters, two frequency mixers (multiplier), the second single-pole double-throw switch (SPDT), intermediate frequency process passage, analog to digital converter and main control chips; Main control chip controls the first single-pole double-throw switch (SPDT) and the second single-pole double-throw switch (SPDT) respectively, and by variable local oscillator model calling the 3rd single-pole double-throw switch (SPDT), the 3rd single-pole double-throw switch (SPDT) connects described two frequency mixers respectively.Described two preamplifier filters comprise first passage preamplifier filter and second channel preamplifier filter, separately corresponding connection the first frequency mixer and the second frequency mixer.Described variable local oscillator module comprises the direct digital synthesiser, the first hilted broadsword four throw switch, four groups of frequency multiplication filtering and amplifying circuits and the second hilted broadsword four throw switch that connect successively, wherein direct digital synthesiser receives the DDS frequency control signal that main control chip sends, and the first hilted broadsword four throw switch and the second hilted broadsword four throw switch receive the switch controlling signal that main control chip sends.Described frequency multiplication filtering and amplifying circuit comprises the first amplifier, multiplier frequency multiplication, the first filter, the second amplifier and the second filter that connect successively.Described intermediate frequency process passage comprises the first amplifilter, three-mixer, the second amplifilter and the logarithmic detector that connect successively.

This receiver changes the frequency of output signal by DDS frequency adjustment word, and by the rapid frequency multiplication of what frequency multiplication to required local oscillator, then exported the amplitude of corresponding frequency by process such as mixing, down-conversion, detections, to realize the function of spectrum monitoring.Owing to adopting frequency doubling technology to realize variable local oscillator, make this receiver in 1ms interscan 4GHz bandwidth, signal capture probability can be significantly improved.The utility model has following remarkable advantage: (1) frequency hopping speed is fast; (2) signal capture probability is high; (3) cost is low, and the construction cycle is short.

Embodiment 1

Utility model works principle is as follows:

(1) FPGA is by SPI interface by a certain frequency adjustment word write DDS register, outputs signal switch to new frequency (f to make DDS _out) and resident a period of time.F _outfollowing relation is had with frequency adjustment word (FTW) and DDS system clock (SYSCLK).

f _out＝FTW×SYSCLK/2 ^N

Wherein, N is the bit wide of FTW.DDS just can be switched to new rate-adaptive pacemaker sine wave signal through several system clock cycle (about tens nanoseconds).

(2) sine wave signal exported by DDS is through what frequency multiplication and after filtering, frequency multiplication to required frequency as receiver mixing local oscillator.Every one-level frequency multiplication is X2 or X4, for 2 frequencys multiplication, if primary signal is:

v _c(t)＝v _scosωt

Wherein, v _sfor signal amplitude, ω is signal angular frequency.Then obtain after X2 frequency multiplication

$v_b\left(t\right)=v_c^2\left(t\right)=\frac{1}{2}{\mathrm{kv}}_s^2(1+cos2\mathrm{\ω}t)$

Wherein, k is Clock Multiplier Factor.

Different from utilizing phase-locked loop (PLL) frequency multiplication, utilize frequency multiplier frequency multiplication must add band pass filter after frequency multiplier.If the electromagnetic spectrum of monitoring is very wide, then must adopt multiple Channel fragment process, switch between multiple passage and utilize FPGA directly to control.Compared with phase-locked loop, frequency multiplication process required time can be ignored.

(3) this variable local oscillator and antenna channels after filtering, amplify after radiofrequency signal carries out mixing, filtering obtains the high intermediate frequency narrow band signal that centre frequency is 2.14GHz.

(4) the high intermediate frequency narrow band signal of 2.14GHz again with one fixing local oscillator (frequency is 2GHz) carry out mixing and filtering, export the low intermediate frequency signal of 140MHz.

(5) low intermediate frequency signal of 140MHz is again through logarithmic detector outputting video signal.

(6) vision signal adopts formation digital signal to deliver to FPGA through ADC.

(7) FPGA carries out integration to vision signal in residence time section, obtains the energy information of respective radio-frequency frequency.

(8) return the first step, repeat above operation, just can obtain the electromagnetic signal emittance in interested spectral range.

Using the low-frequency sine of DDS output as frequency source, the mode utilizing frequency multiplier to add filter obtains required local frequency source of secondary.Owing to have employed the mode of frequency multiplier frequency multiplication, can instantaneous-locking local frequency, receiver can be realized fast frequency-hopped, and sweep complete frequency range within a short period of time.

The whole receiver of the present embodiment switches to two passages by microwave switch and receives.First intermediate frequency adopts the high intermediate frequency of 2.14GHz, and the second intermediate frequency adopts 140MHz Low Medium Frequency, and intermediate-frequency filter adopts Surface Acoustic Wave Filter, to improve whole receiver Out-of-band rejection performance.

In the present embodiment, described control method and process adopt and well known to a person skilled in the art that namely prior art can realize, and are not essential features of the present utility model.

Embodiment 2

For X-band (8-12GHz), receiver frequency hopping search procedure in 4GHz bandwidth is described.Whole receiver is divided into two receive paths by microwave switch, and passage 1 searches for 8-10GHz, and passage 2 searches for 10-12GHz, as shown in Figure 3.

For 8-10GHz passage, passage 1 amplification filtering unit is formed by two groups of amplifiers+filter cascade.Preamplifier adopts the microwave broadband integrated amplifier of Hittite company, and its typical index is as follows:

working frequency range: 7-14GHz;

gain: 17dB;

noise factor: 2.5dB.

Filter is in order to filter out-band outer clutter, Image interference.Filter adopts microstrip interdigital filter form, and dielectric-slab adopts Rogers 4350B.

Local frequency adopts high local oscillator pattern, and variable local oscillator module reference frequency output is 10.14-12.14GHz, and output frequency stepping is 10MHz.The frequency multiplication progression of variable local oscillator inside is decided to be 32 grades, is formed by 24 frequencys multiplication and 12 frequency multiplication cascade.Therefore, DDS reference frequency output is 316.875-379.375MHz.DDS adopts the AD9910 of AD company, and the highest output frequency of this chip can reach 450MHz, and frequency accuracy reaches 0.23Hz.The stepping of variable local oscillator module output frequency is 10MHz, and owing to have employed 32 grades of frequencys multiplication, therefore, the output frequency stepping of AD9910 is 312.5kHz.By actual measurement, whole channel gain is greater than 15dB, and flatness is better than 2dB, and mirror image suppresses to be greater than 40dB.

The radio frequency of 8-10GHz is after the 10.14-12.14GHz signal mixing exported with variable local oscillator, and obtain 2.14GHz height intermediate frequency narrow band signal through band pass filter, bandwidth is 10MHz.Bandpass filtering adopts high q-factor Surface Acoustic Wave Filter, effectively improves Out-of-band rejection ability, and suppresses adjacent-channel interference.Logarithmic detector adopts the high performance logarithmic amplifier AD8310 of AD company, and leading indicator is as follows:

logarithmic range: be greater than 80dB;

log error: be less than 1dB;

the logarithmic response time: be less than 15ns;

log slope: 24mv/dB.

Whole radio-frequency front-end is placed in three different shielding boxs, adopts semi-rigid cable to connect, to reduce mutual crosstalk.By actual measurement, its logarithmic detector tangential sensitivity is better than-80dBm.

When switching to passage 2 and searching for 10-12GHz, adopt low local oscillator pattern, variable local oscillator reference frequency output is 7.86-9.86GHz, and frequency step is still 10MHz.Variable local oscillator module adopts 4 passage bridge modes, as shown in Figure 1.When searching for for X-band frequency hopping, from top to bottom, each passage reference frequency output is respectively 7.86-8.86GHz, 8.86-9.86GHz, 10.14-11.14GHz and 11.14-12.14GHz, and passage bridge is controlled by main control chip FPGA.

Assuming that the operating frequency of FPGA is 50MHz (cycle 20ns), FPGA by serial mode, frequency adjustment word is write DDS.The frequency adjustment word of control DDS output frequency 32 altogether, adds 8 bit address, altogether 40 bit data write DDS, also namely FPGA be DDS write frequency regulate word total time be about 800ns.The process such as frequency multiplication, amplification, filtering of signal is almost complete instantaneously.If be decided to be 1us the integration time of signal, and consider some frequency crank-up times, then the write operation of frequency adjustment word and signal integration need about 2.5us altogether.So 400 frequency saltus steps only need 1ms in one week altogether.

In the present embodiment, described control method and process adopt and well known to a person skilled in the art that namely prior art can realize, and are not essential features of the present utility model.

Claims (5)

1. the fast frequency-hopped receiver in the broadband based on DDS, it is characterized in that, comprise the first single-pole double-throw switch (SPDT) connected successively, two preamplifier filters, two frequency mixers, the second single-pole double-throw switch (SPDT), intermediate frequency process passage, analog to digital converter and main control chips; Main control chip controls the first single-pole double-throw switch (SPDT) and the second single-pole double-throw switch (SPDT) respectively, and by variable local oscillator model calling the 3rd single-pole double-throw switch (SPDT), the 3rd single-pole double-throw switch (SPDT) connects described two frequency mixers respectively.

2. the fast frequency-hopped receiver in a kind of broadband based on DDS according to claim 1, it is characterized in that, described two preamplifier filters comprise first passage preamplifier filter and second channel preamplifier filter, respectively corresponding first frequency mixer and the second frequency mixer.

3. the fast frequency-hopped receiver in a kind of broadband based on DDS according to claim 1, it is characterized in that, described variable local oscillator module comprises the direct digital synthesiser, the first hilted broadsword four throw switch, four groups of frequency multiplication filtering and amplifying circuits and the second hilted broadsword four throw switch that once connect, wherein direct digital synthesiser receives the DDS frequency control signal that main control chip sends, and the first hilted broadsword four throw switch and the second hilted broadsword four throw switch receive the switch controlling signal that main control chip sends.

4. the fast frequency-hopped receiver in a kind of broadband based on DDS according to claim 3, it is characterized in that, described frequency multiplication filtering and amplifying circuit comprises the first amplifier, multiplier frequency multiplication, the first filter, the second amplifier and the second filter that connect successively.

5. the fast frequency-hopped receiver in a kind of broadband based on DDS according to claim 1, is characterized in that, described intermediate frequency process passage comprises the first amplifilter, three-mixer, the second amplifilter and the logarithmic detector that connect successively.