CN104242980B - The design of a kind of Sub-1G RF front-end circuit based on RF energy measuring and parameter regulation means - Google Patents

Abstract

The invention discloses the design of a kind of Sub 1G RF front-end circuit based on RF energy measuring and parameter regulation means, wherein, based on RF energy measuring, the step adjusting the device parameter values in Some Second Order Elliptic function low pass filter specifically includes following steps: obtain channel power values；Calculate wireless signal energy loss on transmission line and internodal communication distance；According to the energy loss on the transmission line calculated and internodal communication distance, adjust the device parameter values of Some Second Order Elliptic function filter.Sub 1G RF front-end circuit stability and the reliability of present invention design are high, and can be based on RF energy measuring, adjust the device parameter values in Some Second Order Elliptic function low pass filter, impedance and the radio frequency source matches impedances of transmission line and load is reached, it is achieved that the transmission of maximum transmission power by changing the actual electronic element value in radio circuit.

Description

The design of a kind of Sub-1G RF front-end circuit based on RF energy measuring and parameter adjustment Method

Technical field

The present invention relates to radio frequency arts, particularly to a kind of Sub-1G RF front-end circuit based on RF energy measuring Design and parameter regulation means.

Background technology

Sub-1G frequency range is that the application section of exempting from of our country launches reception frequency, can be used directly, and penetrance is strong, it is adaptable to The application that barrier is more, needs are wirelessly transferred.Sub-1G can be subdivided into again according to wireless transmission band 433MHz, 470MHz, Tetra-series of 868MHz, 915MHz.Compared to 2.4G frequency range, Sub-1G frequency range is better between coverage effect and capacity, It is widely used in mobile communication and field of wireless at present.

Existing RF front-end circuit general structure is complicated, and stability and the reliability of system are low, the power on transmission line Loss is big, and the device parameter values in circuit is that theory calculates, and actual effect is the most undesirable, and prior art is not deposited Technical scheme in the adjustment of the device parameter values to RF front-end circuit.Therefore, existing RF front-end circuit design structure Unreasonable, and based on the device parameter values of RF energy measuring adjustment circuit, thus can not can not realize maximum transmission power Transmission.

Can effectively design Sub-1G RF front-end circuit accordingly, it would be desirable to a kind of and the ginseng of component can be adjusted The method of number.

Summary of the invention

To this end, the present invention proposes the design of a kind of Sub-1G RF front-end circuit based on RF energy measuring and parameter adjustment side Method, can eliminate the one or more problems caused due to restriction and the defect of prior art fully.

Additional advantages of the present invention, purpose and characteristic, a part will be elucidated in the following description, and another portion Divide for those of ordinary skill in the art by the investigation of description below be will be apparent from or from the enforcement of the present invention Acquire.Can realize by the structure particularly pointed out in the specification and claims of word and accompanying drawing and obtain the present invention Purpose and advantage.

The invention provides the design of a kind of Sub-1G RF front-end circuit based on RF energy measuring and parameter regulation means, Described method specifically includes following steps:

Step 1, the width of the transfer wire in calculating Sub-1G RF front-end circuit；

Step 2, designs Some Second Order Elliptic function low pass filter, and described Some Second Order Elliptic function low pass filter is by 2 resonance Inductance, 2 resonant capacitances and 3 coupling electric capacity compositions, wherein, the first resonant inductance (L1) and the first resonant capacitance (C1) are in parallel Form a LC parallel resonator, the second resonant inductance (L2) and the second resonant capacitance (C2) formation in parallel 2nd LC parallel resonance Device, between a LC parallel resonator and the first port by first coupling electric capacity (C3) ground connection, a LC parallel resonator and By the second coupling electric capacity (C4) ground connection between 2nd LC parallel resonator, logical between the 2nd LC parallel resonator and the second port Cross the 3rd coupling electric capacity (C5) ground connection；

Step 3, design L-type matching network also calculates electric capacity and the reference value of inductance in L-type matching network；

Step 4, based on RF energy measuring, adjusts the device parameter values in Some Second Order Elliptic function low pass filter；Described step Rapid 4 specifically include following steps:

Step 4.1, obtains channel power values；

Step 4.2, calculates wireless signal energy loss on transmission line and internodal communication distance；

Wherein, calculate energy loss by formula PL=P (T)-P (R), wherein, energy when P (T) is to send data Value, P (R) is the energy value receiving data；The PL calculated is substituted into below equation to calculate internodal communication distance:

PL=32.44+20*log (d) km+20*log (f) MHz, wherein, frequency f is 433MHz；

Step 4.3, according to the energy loss on the transmission line calculated in step 4.2 with internodal communicate away from From, adjust the device parameter values of Some Second Order Elliptic function filter.

Preferably, described step 1 specifically includes: according to the width w of below equation calculating transfer wire:

$Z_0=\left(\frac{Z_f}{2\mathrm{\π}*\sqrt{{\mathrm{\ϵ}}_{\mathrm{eff}}}}\right)*\ln (8*\frac{h}{w}+\frac{w}{4h})$

Wherein, Z₀=50 Ω, it is the characteristic impedance of the transmission line in desired Sub-1G RF front-end circuit,For the natural impedance of free space, h is the thickness of pcb board, ε_effIt is by having that following computing formula is given Effect dielectric constant:

${\mathrm{\ϵ}}_{\mathrm{eff}}=\frac{{\mathrm{\ϵ}}_r+1}{2}+\frac{{\mathrm{\ϵ}}_r-1}{2}[{(1+12\frac{h}{w})}^{-1/2}+0.04*{(1-\frac{w}{h})}^2].$

Preferably, described step 2 specifically includes:

Step 2.1, knows each normalized parameter value g1 of Some Second Order Elliptic function filter prototype, g2, g3 according to tabling look-up；

Step 2.2, calculates normalized coupling coefficient k₁₂...k_n-1,n, wherein,Wherein n=3；

Step 2.3, calculates wave filter coefficient of coup K₁₂...K_n-1,n, wherein,N=3, wherein, △ f is bandwidth, f₀Centered by frequency；

Step 2.4, the value of the resonant inductance (L1, L2) of suitable selective resonance device；

Step 2.5, calculates the port identity impedance of the first port and the second port, wherein:

The characteristic impedance computing formula of the first port is:

The characteristic impedance computing formula of the second port is:N=3；

Step 2.6, calculates value C of the resonant capacitance (C1, C2) of resonator according to following formula_resonator:

$C_{\mathrm{resonator}}=\frac{1}{{\mathrm{\ω}}_0^2*L_{\mathrm{resonator}}}=\frac{1}{{\left(2\mathrm{\π}{f}_0\right)}^2*L_{\mathrm{resonator}}};$

Step 2.7, calculates the value of each coupling capacitor (C3, C4, C5) according to following formula, really calculate (C3, Or the value of (C4, C5) C4):

C₁₂=K₁₂C_resonator, C_n-1,n=K_n-1,nC_resonator, n=3；

When actual design elliptic function filter, typically make C3=C5.

Step 2.8, is transformed into required characteristic impedance by port Impedance.

Preferably, in step 2.4, the resonant inductance value of selection is 6.8nH.

Preferably, in step 2.8, required characteristic impedance is 50 Ω.

Preferably, by reading the energy value field of the depositor of microcontroller and the energy value read being converted to letter Number intensity, obtains channel power values.

Preferably, the device parameter values adjusting Some Second Order Elliptic function filter described in step 4.3 farther includes: first First adjust the value adjusting resonant inductance L1 or L2 with 0.2NH for adjusting step-length, then adjust with 0.3PF or 0.4PF for adjusting step-length The value of whole coupling electric capacity C3 or C5.

Sub-1G RF front-end circuit stability and the reliability of present invention design are high, it is possible to based on RF energy measuring, Adjust the device parameter values in Some Second Order Elliptic function low pass filter, come by changing the actual electronic element value in radio circuit Reach impedance and the radio frequency source matches impedances of transmission line and load, it is achieved that the transmission of maximum transmission power.

Accompanying drawing explanation

Fig. 1 is the module map of the Sub-1G RF front-end circuit according to the embodiment of the present invention.

Fig. 2 a shows that the attenuation change of elliptic function, binomial (Butterworth) and chebyshev low-pass filter is bent Line.

Fig. 2 b shows Some Second Order Elliptic function low pass filter model of the present invention.

Fig. 3 shows each electronic element value in Some Second Order Elliptic function low-pass filter circuit according to embodiments of the present invention Specific design step.

Fig. 4 is that the L-type matching network according to the embodiment of the present invention designs a model.

Fig. 5 be according to the embodiment of the present invention, based on RF energy measuring, adjust in Some Second Order Elliptic function low pass filter The flow chart of device parameter values.

Detailed description of the invention

With reference to the accompanying drawings the present invention is described more fully, the exemplary embodiment of the present invention is wherein described.

RF front-end circuit connects antenna.Antenna is the important electronic unit of one of wireless device transceiving electromagnetic ripple signal. The communication engineering systems such as either radio communication, broadcast, TV, radar, navigation, electronic countermeasure, remote sensing, every utilize electromagnetism Ripple transmits information, and antenna will be relied on to be operated.Therefore, radio-frequency antenna is also to closing weight for radio node communication , the quality of Antenna Design will be directly connected to wireless signal tranception-quality, affect the reception and transmission range of wireless signal.

The most common antenna mainly has PCB antenna, Chip antenna and Whip antenna.Wherein, PCB antenna cost Relatively low, but design difficulty is relatively big, needs the less radio-frequency many factors considered；Chip antenna, i.e. ceramic antenna, volume is little, becomes This is moderate, is suitable for the application scenarios of relatively short distance communication；Whip antenna performance is best, and wireless signal amplification effect is obvious, Cost is of a relatively high.

Consider that signal gain, impedance matching, channel width, node size, communication is stable and the factor such as cost, this Bright preferred selection meets the Whip antenna of SMA (SubMiniature Version A) standard interface as the wireless joint of SD-WSN The radio-frequency antenna of point, to adapt to the needs of different application scenarios, but, PCB antenna and the equally applicable present invention of Chip antenna.

The Sub-1G radio circuit of the present invention have employed KW01 radio frequency chip, inside KW01 radio frequency chip It is integrated with the rf receiver and transmitter SX1233 worked under Sub-1GHz radio band, compares Freescale company and previously released Other ZigBee radio frequency chips for, its wireless receiving and dispatching is apart from farther.Meanwhile, it has been internally integrated two-way level in view of it Connection, unidirectional power amplifier, low-noise amplifier, so when designing the RF front-end circuit of radio node, it is not necessary to consider to adopt With extending out power amplifier and low-noise amplifier strengthens the gain of wireless signal to increase the design side of wireless transmission distance Case.Meanwhile, rf receiver and transmitter SX1233 can support two kinds of wireless receiving and dispatching mode of operations: calibration power output mode and enhancing Power mode output, transmits, for user's high-power wireless, the mode that provides more choices.

It addition, antenna can be divided into again single ended antenna and differential antennae.Single ended antenna is also called unbalanced antennas, difference sky Line is also called balancing antenna.MC1321X, MC1322X of releasing before KW01 radio frequency chip and Freescale company and The differential antennae that the ZigBee radio frequency chip of MC1323X series is used is different, and KW01 uses single ended antenna interface. Therefore, there is no need to use balun (balance/imbalance transformator) circuit to carry out positive and negative change in voltage.It is wireless that this will simplify SD-WSN The hardware designs of Sub-1G less radio-frequency front-end circuit in node, reduces the design complexities of RF hardware, shortens chip application Construction cycle.Wherein, single ended antenna rely primarily on (ground) be generally 50 Ω as reference signal, its characteristic impedance.

Fig. 1 shows the module map of Sub-1G RF front-end circuit.Design according to embedded system hardware componentization is former Then, and consider multiple radio circuits such as signal gain, characteristic impedance coupling, low-pass filtering, signaling reflex and radiation patterns Design considerations, the mode that the present invention uses Some Second Order Elliptic function low pass filter to combine double L-shaped matching network designs radio-frequency front-end Circuit, gives the module map of Sub-1G RF front-end circuit as shown in Figure 1.In addition to the module shown in Fig. 1, Sub-1G RF front-end circuit also includes the modules such as radio frequency chip, Some Second Order Elliptic function low pass filter and double L-shaped matching networks, its In, Some Second Order Elliptic function low pass filter is connected with radio frequency chip, and it is mainly used in the characteristic frequency in high-frequency signal Or the frequency component in frequency range does and strengthens or attenuation processing；Double L-shaped matching networks are arranged on and draw at radio-frequency antenna and transmitting-receiving multiplexing Between foot RFIO and high-power transmitting terminal pin PA_BOOST, to provide rational characteristic impedance coupling, stopband suppression, reduce and pass Power attenuation on defeated line, improves and launches power capacity.Annexation between each device above-mentioned is to those skilled in the art For be known, and present invention is primarily targeted at Some Second Order Elliptic function low pass filter and double L-shaped matching networks Design and parameter adjustment aspect, therefore, for the purpose simply clearly illustrated, Fig. 1 is not specifically illustrated in wireless penetrating Frequently the original paper such as chip, Some Second Order Elliptic function low pass filter and double L-shaped matching networks.

Sub-1G RF front-end circuit shown in Fig. 1 passes through software arrangements, can realize two kinds of wireless receiving and dispatching mode of operations Switching.Wherein, the first frequency selection circuit 13 is connected with first antenna 11 by the electric capacity of 10pF, and the second frequency selection circuit 14 passes through 10pF Electric capacity be connected with first antenna 12, the first frequency selection circuit 13 and the second frequency selection circuit 14 are mainly used in selecting useful signal Frequently, glitch-free signal is exported.VR_PA (RF) pin blocks passive network 15 by the first AC and the second AC blocks After passive network 16, the power amplifier PA for transmitting terminal provides pulsation-free pure power supply.When being in calibration power output mould During formula, KW01 chip mainly carries out the transmitting-receiving of wireless signal by RFIO pin.In this mode, it is possible to provide-18dBm to+ Power output in the range of 13dBm, by software arrangements, the increment of minimum power regulation is 1dB.When being in enhancing power output Pattern, RFIO pin is used as signal receiving end, and PA_BOOST pin is used as high-power signal transmitting terminal, by programmed configurations, Changeable PA_BOOST end is two-way cascade or unidirectional emission power enhancement mode.Under strengthening power mode output, it is possible to provide- Power output in the range of 18dbm to+17dBm.

The emphasis of the present invention is that design Sub-1G RF front-end circuit, and based on the RF energy measuring parameter to circuit It is adjusted.It will be described in detail below.

A kind of based on RF energy measuring Sub-1G RF front-end circuit design proposed by the invention and parameter adjustment side Method, mainly comprises the steps that

Step 1, the width of the transfer wire in calculating Sub-1G RF front-end circuit.

The KW01 radio frequency chip that the present invention uses works in the radio band of below 1GHz, and this radio band belongs to special High frequency (UHF), its wavelength is typically with cm as linear module.So, in radio circuit, when radio wavelength and discrete electronics unit When the geometric size of part and the deposited copper conductor length of PCB are comparable, the characteristic impedance of transmission line can be produced, increase the spoke of circuit Penetrate loss, reduce the transmitting output of radio frequency source.Therefore, when drawing the PCB figure of RF front-end circuit, rationally select to apply copper The trace width of wire will change the characteristic impedance of transmission line, when its characteristic impedance with radio frequency source matches time, and can Launch power attenuation with effective reduction, thus improve the reception and transmission range of radio node.

Approximate representation formula according to characteristic of semiconductor impedance, public in combination with kirchhoffs law theory Formula, as first approximation, supposes that compared with the thickness h of pcb board the thickness t of circuit can ignore that, in this case, and Wo Menke Utilize and circuit relative dimensions (w and h) and DIELECTRIC CONSTANT ε_rRelevant empirical equation, can obtain the transfer wire in general PCB Characteristic impedance Z₀For:

$Z_0=\left(\frac{Z_f}{2\mathrm{\π}*\sqrt{{\mathrm{\ϵ}}_{\mathrm{eff}}}}\right)*\ln (8*\frac{h}{w}+\frac{w}{4h})---\left(1.1\right)$

Wherein,For the natural impedance of free space, w is the width of transfer wire, and h is the thickness of pcb board Degree, ε_effIt is the effective dielectric constant be given by following formula computing formula:

${\mathrm{\ϵ}}_{\mathrm{eff}}=\frac{{\mathrm{\ϵ}}_r+1}{2}+\frac{{\mathrm{\ϵ}}_r-1}{2}[{(1+12\frac{h}{w})}^{-1/2}+0.04*{(1-\frac{w}{h})}^2]---\left(1.2\right)$

In actual applications, the radio-frequency source signal line impedence within general radio frequency chip is 50 Ω or 200 Ω (can select Selecting, typically we select 50 Ω), in order to the characteristic impedance with radio frequency source matches, it is desirable to the transmission line in radio circuit Need the characteristic impedance Z having₀Also it is 50 Ω (definite value), therefore can be according to actual Jie corresponding to selected pcb board material type Electric constant ε_r(being determined by pcb board material provider, be the most also definite value), thickness h (adjustable value) and wireless frequency (definite value, this Invention is for 433MHz wireless frequency), in combination with transfer wire width w and PCB thickness than the law curve between w/h, can Try to achieve the design width w of required transmission line, thus reduce the wire transmission power attenuation of radio system.

Table 1-1 lists the parameter that controls of impedance (50 Ω) of some typical case PCB:

The parameter that typical case under table 1-1 characteristic impedance (50 Ω) controls

Step 2, designs Some Second Order Elliptic function low pass filter.

When designing radio circuit, the characteristic frequency in high-frequency signal or the frequency component in frequency range are done and strengthens or decay Process is individual particularly significant, therefore, designs suitable wave filter most important.

According to Basis Theory of Circuit, wave filter can be divided into low pass, high pass, band logical and the big class of band elimination filter four.Pin Variety classes to wave filter, the following parameter characteristic of main consideration:

(1) RF insertion loss: in the ideal case, the wave filter being inserted in radio circuit, should be at its free transmission range Other power attenuations of interior introducing.But, in actual applications, it is impossible to eliminate wave filter power attenuation intrinsic, to a certain degree. Insertion loss can describe the difference of power response amplitude and 0dB benchmark quantitatively, and its mathematic(al) representation is:

$\mathrm{IL}=10\log \frac{P_{\mathrm{in}}}{P_L}=-10\log (1-{\left|F_{\mathrm{in}}\right|}^2)---\left(1.3\right)$

Wherein, P_LIt is the wave filter power to load output, P_inThe input power that obtains from signal source of wave filter, be from The wave filter reflection coefficient to signal source.

(2) return loss: be also called reflection loss.In high-frequency circuit, reflect owing to transmission line impedance is not mated And the ratio of the incidence wave energy reflection produced.

(3) ripple: the filter theory knowledge from radio circuit understands, by the ripple coefficient of definition to describe passband The flatness of interior signal response, and to use dB be the difference that unit represents the maxima and minima of response amplitude.

(4) bandwidth: define wave filter upper side frequency and the difference on the frequency of lower side frequency to corresponding to 3dB attenuation in passband Value:

BW^3dB=f_U ^3dB-f_L ^3dB (1.4)

(5) squareness factor: this index is the ratio of 60dB bandwidth and three dB bandwidth, which depict wave filter at cut-off frequency The steep of neighbouring response curve change:

$\mathrm{SF}=\frac{{\mathrm{BW}}^{60\mathrm{dB}}}{{\mathrm{BW}}^{3\mathrm{dB}}}=\frac{{f_U}^{60\mathrm{dB}}-{f_L}^{60\mathrm{dB}}}{{f_U}^{3\mathrm{dB}}-{f_L}^{3\mathrm{dB}}}---\left(1.5\right)$

(6) stopband suppression: in the ideal case, be intended to wave filter and there is in stopband frequency range infinitely-great attenuation. But, in the design of actual radio frequency circuit, typically can only obtain the limited attenuation relevant to filter element number.In reality In the application of border, contact to make stopband suppression set up with squareness factor, the Reference Design value generally suppressed using 60dB as stopband.

On the premise of the fully three kinds of filter attenuation coefficients of the reference graph of relation with wireless frequency, in conjunction with KW01 core The radiofrequency characteristics of sheet rf receiver and transmitter SX1233, in the design part employing elliptic function low pass filtered to RF front-end circuit Ripple device.Fig. 2 a compared for elliptic function, binomial (Butterworth) and the attenuation change curve of chebyshev low-pass filter.Its In, Butterworth filter has the attenuation curve of dullness, is easier to realize, but wants in passband and resistance in actual design Realizing precipitous transkit attenuation change between band, then need more discrete electronic component, this can increase cost of hardware design；Cut Can obtain preferable abrupt transition attenuation curve than snow husband's wave filter, the attenuation curve in passband has fluctuating to a certain degree (being ripple), and the ripple of its attenuation curve keeps equal amplitude in passband or stopband；Compare first two wave filter, Elliptic function filter transition change between passband and stopband is the most precipitous, and shortcoming is that it has ripple shadow at two ends Ring.

In order to be reduced as far as radio frequency peripheral cell quantity, reduce transmission line loss, and make wave filter keep good Cut-off frequency characteristic, the present invention uses Some Second Order Elliptic function low-pass filtering as shown in Figure 2 b when designing RF front-end circuit Device.As shown in Figure 2 b, Some Second Order Elliptic function low pass filter of the present invention by 2 resonant inductances, 2 resonant capacitances and 3 coupling electric capacity compositions, wherein, the first resonant inductance (L1) and the first resonant capacitance (C1) formation in parallel oneth LC parallel resonance Device, the second resonant inductance (L2) and the second resonant capacitance (C2) are in parallel forms the 2nd LC parallel resonator, a LC parallel resonance By the first coupling electric capacity (C3) ground connection between device and the first port, a LC parallel resonator and the 2nd LC parallel resonator it Between by second coupling electric capacity (C4) ground connection, between the 2nd LC parallel resonator and the second port by the 3rd coupling electric capacity (C5) Ground connection.

Owing to elliptic filter transfer function is a kind of more complicated approximating function, traditional method for designing is utilized to carry out electricity Road network is comprehensively analyzed to be needed to carry out relatively complicated mathematical calculation.Therefore the present invention utilizes computation of table lookup method, consults second order Each normalized value in the elliptic function low pass filter model of 0.1dB ripple, and according to required wireless signal center Frequency and bandwidth calculate normalized coupling coefficient and the wave filter coefficient of coup respectively, thus select suitable resonant inductance value.So After, calculate each capacitance (including resonant capacitance and coupling capacitance) successively and combine the characteristic impedance value of front network port Convert, finally give calculated value.

The specific design step of each electronic element value in Some Second Order Elliptic function low-pass filter circuit is as shown in Figure 3. Shown in Fig. 3, step 2 specifically includes following sub-step:

Step 2.1, knows each normalized parameter value g1 of Some Second Order Elliptic function filter prototype, g2, g3 according to tabling look-up；

Table 1-2 lists the normalized parameter value of each element corresponding to Fig. 2 b elliptic function filter.

In table 1-2 band, relief volume is each element normalized value of elliptic function filter during 0.1dB

When designing elliptic function filter, first have to the target clearly designed, it is assumed that we need to design a center Frequency f₀For 433MHz, bandwidth If be 2MHz (± 1MHz), characteristic impedance be the Some Second Order Elliptic function filter of 50 Ω.As setting The first step of meter, first has to the normalized component value under stop-band frequency is as 2MHz in table 1-2 as foundation, try to achieve one group with The required identical parameter of design, Some Second Order Elliptic function filter should have 3 parameters, and making it is that (gn is n-1 rank with g3 for g1, g2 The parameter of high pass filter).This g1, g2 are equal to normalized component value (C3, C1 in corresponding diagram 2b respectively with the value of g3 With L1).

Step 2.2, calculates normalized coupling coefficient k₁₂...k_n-1,n, wherein,Wherein n=3；

In step 2.2, Some Second Order Elliptic function filter is by 2 resonators (C1 Yu L1, C2 Yu L2 institute group in Fig. 2 b Become resonator) and 3 bonder k (C3, C4 and C5) formed, we obtain one group of normalization according to g1, g2 with g3 and couple Coefficient k 12, k23.

Step 2.3, calculates wave filter coefficient of coup K₁₂...K_n-1,n, wherein,N=3, wherein, △ f is bandwidth, f₀Centered by frequency；

In step 2.3, Some Second Order Elliptic function filter is by 2 resonators (C1 Yu L1, C2 Yu L2 institute group in Fig. 2 b Become resonator) and 3 bonder k (C3, C4 and C5) formed, we obtain one group of normalization according to g1, g2 with g3 and couple Coefficient k 12, k23.

Step 2.4, the value of the resonant inductance (L1, L2) of suitable selective resonance device；

In step 2.4, suitably choose the inductance value (L1, L2) of LC parallel resonator, according to designer's experience, generally About 10nH, there is no absolute requirement, currently preferred employing 6.8nH, i.e. L1 and L2 in corresponding diagram 2b.

Step 2.5, calculates the port identity impedance of the first port and the second port, wherein:

The characteristic impedance computing formula of the first port is:

The characteristic impedance computing formula of the second port is:N=3.

Step 2.6, according to the value of the resonant capacitance (C1, C2) of following formula calculating resonator:

$C_{\mathrm{resonator}}=\frac{1}{{\mathrm{\ω}}_0^2*L_{\mathrm{resonator}}}=\frac{1}{{\left(2\mathrm{\π}{f}_0\right)}^2*L_{\mathrm{resonator}}},$ Wherein, C_resonatorIt it is resonant capacitance value (that is, first Resonant capacitance (C1) and the value of the second resonant capacitance (C2)), in the present invention, the first resonant capacitance (C1) and the second resonant capacitance (C2) value is identical.

Step 2.7, calculates each coupling capacitor values according to following formula:

C₁₂=K₁₂C_resonator, C_n-1,n=K_n-1,nC_resonator, n=3.

Because comprising two coefficient of coup K12 and K23 in circuit, but the two coefficient of coup can not come as coupling element For realizing coupling filter, so wave filter to be realized, K12 with K23 must be changed into and couple capacitor, C12=K12* Cresonator, C23=K23*Cresonator.(C3, C4 or C4 in corresponding diagram 2b, C5).

Step 2.8, is transformed into required characteristic impedance by port Impedance；

Resonance coupling parameter out designed by above, in its Fig. 2 b, the impedance of two ends Port is respectively Z1 and Z2, not Being 50 desired Ω, so we also need to be changed into desired value, carrying out impedance transformation is exactly first to try to achieve the two feature The ratio K of impedance, then removes each capacitance in Fig. 2 b, goes to take advantage of each inductance value in Fig. 2 b circuit with K with K.

So far, we have just obtained impedance is all electric capacity in the elliptic function filter circuit under 50 Ω, electricity Inductance value, the most just completes the design of Some Second Order Elliptic function low pass filter.

Step 3, design L-type matching network also calculates electric capacity and the reference value of inductance in L-type matching network.

Fig. 4 show the simple L-type matching network being made up of electric capacity and two discrete electronic components of inductance and designs a model, its In, Z_TFor wireless signal at the output impedance of present frequency point, Z_AFor the input impedance of antenna, Z_MIt is then the defeated of L-shaped matching network Go out impedance.In order to realize maximum power transfer between radio signal source and load, need to make the output impedance of signal source and load Impedance conjugation is equal, is Z_MWith Z_AConjugate complex number is equal.Therefore, impedance Z_MValue equal to Z_TAfter in parallel with electric capacity C again with inductance L connects:

$Z_M=\frac{1}{z_T^{-1}+j{B}_C}+j{X}_L---\left(1.6\right)$

Wherein, B_C=wC is the susceptance of electric capacity, X_L=wL is the induction reactance of inductance.Impedance meter by transmitting set Yu antenna It is shown as form (the i.e. Z of real part and imaginary part_T=R_T+jX_tAnd Z_A=R_A+jX_A), then above-mentioned expression formula can be converted into:

$\frac{B_T+j{X}_T}{1+{\mathrm{jB}}_C(R_T+{\mathrm{jX}}_T)}+{\mathrm{jX}}_L=R_A-{\mathrm{jX}}_A---\left(1.7\right)$

By the real part of (3.7 formula) and imaginary part separately, then can get two equations:

R_T=R_A(1-B_CX_T)+(X_A+X_L)B_CR_T (1.8a)

X_T=R_TR_AB_C-(1-B_CX_T)(X_A+X_L) (1.8b)

Obtain the X in (3.8a) formula_LAnd bring (3.8b) formula into and can obtain one about B_CQuadratic equation, its solution is:

$B_C=\frac{X_T\±\sqrt{\frac{R_T}{R_A}(R_T^2+X_T^2)-R_T^2}}{R_T^2+X_T^2}---\left(1.9a\right)$

Due to R_T>R_A, so the value in radical sign on the occasion of and be more thanFor ensure (1.9a) formula be on the occasion of, choose this formula For positive sign.(1.9a) formula substitution (1.8a) formula be can get X_LFor:

$X_L=\frac{1}{B_C}-\frac{B_A(1-B_C{X}_T)}{B_C{R}_T}-X_A---\left(1.9b\right)$

By the parameter during actual design radio circuit, including signal in the output impedance Z of present frequency point_TAnd antenna Input impedance Z_A, (1.9a) and (1.9b) formula of substitution can draw, in L-type matching network, the approximated reference of electric capacity and inductance sets Evaluation.

The combination of Some Second Order Elliptic function low pass filter and double L-shaped matching networks, mainly has a following characteristics:

(1) provide rationally between radio-frequency antenna and transmitting-receiving multiplexing pins RFIO and high-power transmitting terminal pin PA_BOOST Characteristic impedance coupling, stopband suppression, reduce the power attenuation on transmission line, improve and launch power capacity.

(2) in L-shaped match circuit, impedance transformation is carried out by the value using suitable electric capacity and inductance, it is ensured that launch Minimal reflection is formed, it is achieved launch the optimization of power between source and load.

(3) use required element amount less Some Second Order Elliptic function low pass filter design scheme, reduce radio circuit Design complexities while, be effectively increased stability and the reliability of system.

By above description, design the Some Second Order Elliptic function low pass filter in Sub-1G RF front-end circuit Circuit and the circuit of L-type matching network, but the device parameter values in circuit is theory to be calculated, and actual effect is paid no attention to greatly Think.The present invention speculates the reality of Sub-1G front end circuit design each electronic element value of median filter based on energy detection algorithm Value.Transmitting signal intensity according to transmitting node, energy measuring obtains node and receives energy value, utilizes theory and experience to be connected Connect Mass Calculation and go out the reflection coefficient in the design of Sub-1G RF front-end circuit and return loss radio-frequency performance parameter, and by more Change actual electronic element value in radio circuit and reach impedance and the radio frequency source matches impedances of transmission line and load, it is achieved maximum Penetrate the transmission of power.

Below each electronic component parameter adjusted in Some Second Order Elliptic function low pass filter is described in detail.

Step 4, based on RF energy measuring, adjusts the device parameter values in Some Second Order Elliptic function low pass filter；Step 4 has Body comprises the following steps:

Step 4.1, obtains channel energy；

The SX1233 wireless transceiver being internally integrated due to the Sub-1G chip KW01 used can support channel energy The physical layer service functions such as detection, link-quality instruction, clear channel assessment (CCA), so KW01 has the hardware of detection energy Realize, the therefore energy measuring of wireless signal, can be realized by hardware.The signal energy value obtained can be passed through certain by hardware The conversion that calculates be deposited into RssiValue [7:0] the energy value field of RegRssiValue depositor of microcontroller.Signal is strong In degree and depositor, the conversion between RssiValue [7:0] can be by being converted to, i.e.

Enery (R)=-(dec (RssiValue [7:0]/2)) (2)

Wherein the unit of Enery (R) is dBm.In formula, dec represents decimal value.

Step 4.2, calculates wireless signal energy loss on transmission line and internodal communication distance；

Because the value of the depositor RssiValue [7:0] by reading Sub-1G chip KW01, and can by formula (2) To calculate the wireless data received at signal intensity herein.Due to the energy P (T) during known transmission data and reception number According to energy value P (R) (size of the two value is it is known that can regulate by MCU side's software arrangements of KW01 chip), therefore may be used To draw the actual energy loss in the case of transmission range is as D between fixing node.

PL=P (T)-P (R) (3)

In combination with theoretical propagation loss formula LFS=32.44+20*LOG (D) KM+20*LOG (F) MHZ, by analyzing, Between actual energy loss PL and theoretical Propagation of Energy loss LFS, there is linear equivalence relation, therefore PL=LFS can be drawn, i.e.

PL=32.44+20*log (d) km+20*log (f) MHz； (4)

By formula (3), we can obtain PL, meanwhile, the present invention is directed to 433MHZ frequency, therefore f frequency is fixed value 433MHZ, substitutes into known quantity formula (4) and can draw communication distance D.It is above calculating the spacing of two nodes of 433MHZ channel From theoretical basis and be under ideal conditions.But when reality is tested, due to by other electromagnetic waves, barrier, wet The impact of the factors such as degree, temperature, causes the result of test and notional result to have deviation.

Step 4.3, according to the energy loss on the transmission line calculated in step 4.2 with internodal communicate away from From, adjust the device parameter values of Some Second Order Elliptic function filter.

As previously described, because utilize traditional method for designing carry out circuit network comprehensively analyze need to carry out relatively complicated Mathematical calculation, therefore typically utilizes computation of table lookup method when design, consults each normalization in low-pass filter function model Value, and calculate normalized coupling coefficient and the wave filter coefficient of coup respectively according to mid frequency and bandwidth, thus select suitably Ground resonant inductance value.Then, calculate resonant capacitance and each coupling capacitance successively and combine the characteristic resistance of front network port Anti-value converts, and finally gives calculated value.

Meanwhile, radio circuit is optimized by the present invention according to the above-mentioned value of calculation to energy loss, reasonably selects to become Change the component value of capacitor and inductor in Fig. 2 b, during adjustment, should with C3, L1 or C5, L2 for mainly adjusting target, first adjust inductance L1 or The value of L2, and carry out left and right adjustment test with 0.2NH for adjusting step-length, when the inductance value selected makes the transmission of radio node connect Receive energy value and reach one when being the most preferably worth, then adjust C3 or C5, when adjusting electric capacity, with 0.3PF or 0.4PF for adjusting step Long, find the maximum performance point of wave filter, realize the transmission of maximum transmission power as much as possible, it is necessary to make semiconductor circuits And impedance and the radio frequency source matches impedances of load.

Through experimental results demonstrate, in conjunction with MCU side's software of KW01 chip, during reality adjusts, adjust C3 or C5 Value just can get a desired effect, table 1-3 lists the contrast of the value of element before and after adjustment.

Table 1-3Sub-1G RF front-end circuit experiment parameter explanation (as a example by 433MHz)

The present invention need not strengthen antenna, carries out parameter adjustment by measuring energy, can reach the communication distance of 1000 meters, table 1-4 illustrates when 700 meters with 1000 meters of distances, the different packet loss contrasts launching wireless data transceiving under power.From table In it can be seen that circuit element parameter adjust after, wireless data transceiving effect is significantly improved.

Packet transmitting-receiving test result contrast before and after parameter adjustment under table 1-4433MHz

Above content is only presently preferred embodiments of the present invention, for those of ordinary skill in the art, according to the present invention's Thought, the most all will change, and this specification content should not be construed as the present invention Restriction.

Claims (4)

1. Sub-1G RF front-end circuit based on RF energy measuring design and a parameter regulation means, described method is specifically wrapped Include following steps:

Step 1, the width of the transfer wire in calculating Sub-1G RF front-end circuit；

Step 2, design Some Second Order Elliptic function low pass filter, described Some Second Order Elliptic function low pass filter by 2 resonant inductances, 2 resonant capacitances and 3 coupling electric capacity compositions, wherein, the first resonant inductance (L1) and the first resonant capacitance (C1) formation in parallel Oneth LC parallel resonator, the second resonant inductance (L2) and the second resonant capacitance (C2) are in parallel forms the 2nd LC parallel resonator, By the first coupling electric capacity (C3) ground connection, a LC parallel resonator and second between oneth LC parallel resonator and the first port By the second coupling electric capacity (C4) ground connection between LC parallel resonator, by the between the 2nd LC parallel resonator and the second port Three coupling electric capacity (C5) ground connection；

Step 3, design L-type matching network also calculates electric capacity and the reference value of inductance in L-type matching network；

Step 4, based on RF energy measuring, adjusts the device parameter values in Some Second Order Elliptic function low pass filter；Described step 4 has Body comprises the following steps:

Step 4.1, obtains channel power values；

Step 4.2, calculates wireless signal energy loss on transmission line and internodal communication distance；

Wherein, calculate energy loss by formula PL=P (T)-P (R), wherein, energy value when P (T) is to send data, P (R) for receiving the energy value of data；The PL calculated is substituted into below equation to calculate internodal communication distance:

PL=32.44+20*log (d) km+20*log (f) MHz, wherein, frequency f is 433MHz；

Step 4.3, according to the energy loss on the transmission line calculated in step 4.2 and internodal communication distance, adjusts The device parameter values of whole Some Second Order Elliptic function low pass filter.

Sub-1G RF front-end circuit based on RF energy measuring the most according to claim 1 design and parameter adjustment side Method, it is characterised in that described step 1 specifically includes: according to the width w of below equation calculating transfer wire:

$Z_0=\left(\frac{Z_f}{2\mathrm{\π}*\sqrt{{\mathrm{\ϵ}}_{eff}}}\right)*\ln (8*\frac{h}{w}+\frac{w}{4h})$

Wherein, Z₀=50 Ω, it is the characteristic impedance of the transmission line in desired Sub-1G RF front-end circuit,For the natural impedance of free space, h is the thickness of pcb board, ε_effIt is by having that following computing formula is given Effect dielectric constant:

${\mathrm{\ϵ}}_{eff}=\frac{{\mathrm{\ϵ}}_r+1}{2}+\frac{{\mathrm{\ϵ}}_r-1}{2}\[{(1+12\frac{h}{w})}^{-1/2}+0.04*{(1-\frac{w}{h})}^2\].$

Sub-1G RF front-end circuit based on RF energy measuring the most according to claim 1 design and parameter adjustment side Method, it is characterised in that by reading the energy value field of the depositor of microcontroller and the energy value read being converted to letter Number intensity, obtains channel power values.

Sub-1G RF front-end circuit based on RF energy measuring the most according to claim 1 design and parameter adjustment side Method, it is characterised in that the device parameter values adjusting Some Second Order Elliptic function low pass filter described in step 4.3 is wrapped further Include: first adjust and adjust the first resonant inductance L1 or the value of the second resonant inductance L2 with 0.2NH for adjusting step-length, then with 0.3PF or 0.4PF is to adjust step-length to adjust the first coupling electric capacity C3 or the value of the 3rd coupling electric capacity C5.