CN104242980A - Sub-1G radio frequency front-end circuit design based on RF energy detection and parameter adjustment method based on RF energy detection - Google Patents

Abstract

The invention discloses a sub-1G radio frequency front-end circuit design based on RF energy detection and a parameter adjustment method based on RF energy detection. The procedure for adjusting parameter values of components in a second-order elliptic function low-pass filter on the basis of RF energy detection specifically comprises the following steps that a channel energy value is obtained; energy loss of a wireless signal on a transmission line and the communication distance between nodes are calculated; according to the calculated energy loss on the transmission line and the communication distance between the nodes, the parameter values of the components of the second-order elliptic function filter are adjusted. The stability and the reliability of the designed Sub-1G radio frequency front-end circuit are high, the parameter values of the components in the second-order elliptic function low-pass filter can be adjusted on the basis of RF energy detection, the purpose that the transmission line and the impedance of the load are matched with the impedance of a radio frequency source is achieved by replacing the actual electronic component values of the radio frequency circuit, and transmission at the maximum transmission power is achieved.

Description

A kind of design of the Sub-1G radio-frequency (RF) front-end circuit based on RF energy measuring and parameter regulation means

Technical field

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

Background technology

Sub-1G frequency range be our country exempt from application section launch and accept frequency, can directly use, penetrability is strong, is applicable to the application that barrier is more, need wireless transmission.Sub-1G can be subdivided into again 433MHz, 470MHz, 868MHz, 915MHz tetra-series according to wireless transmission band.Compared to 2.4G frequency range, Sub-1G frequency range effect between coverage effect and capacity is better, is widely used in mobile communication and field of wireless at present.

Existing radio-frequency (RF) front-end circuit general structure is complicated, stability and the reliability of system are low, power loss on transmission line is large, and the device parameter values in circuit is theory to be calculated, actual effect is undesirable greatly, and prior art does not exist the technical scheme of the adjustment of the device parameter values of radio frequency front-end circuit.Therefore, existing radio-frequency (RF) front-end circuit project organization is unreasonable, and based on the device parameter values of RF energy measuring Circuit tuning, thus can not can not realize the transmission of maximum transmission power.

Therefore, need a kind ofly can effectively design Sub-1G radio-frequency (RF) front-end circuit and can the method for parameter of Circuit tuning element.

Summary of the invention

For this reason, the present invention proposes the design of a kind of Sub-1G radio-frequency (RF) front-end circuit based on RF energy measuring and parameter regulation means, can eliminate one or more problems that restriction and defect due to prior art cause fully.

Additional advantages of the present invention, object and characteristic, a part will be elucidated in the following description, and another part for those of ordinary skill in the art by being obvious to the investigation of explanation below or acquiring from enforcement of the present invention.Can realize and obtain the object of the invention and advantage by the structure pointed out especially in the specification of word and claims and accompanying drawing.

The invention provides the design of a kind of Sub-1G radio-frequency (RF) front-end circuit based on RF energy measuring and parameter regulation means, described method specifically comprises the following steps:

Step 1, calculates the width of the transfer wire in Sub-1G radio-frequency (RF) front-end circuit;

Step 2, design Some Second Order Elliptic function low pass filter, described Some Second Order Elliptic function low pass filter is by 2 resonant inductances, 2 resonant capacitances and 3 coupling capacitance compositions, wherein, first resonant inductance (L1) and the first resonant capacitance (C1) parallel connection form a LC parallel resonator, second resonant inductance (L2) and the second resonant capacitance (C2) parallel connection form the 2nd LC parallel resonator, by the first coupling capacitance (C3) ground connection between one LC parallel resonator and the first port, by the second coupling capacitance (C4) ground connection between one LC parallel resonator and the 2nd LC parallel resonator, by the 3rd coupling capacitance (C5) ground connection between 2nd LC parallel resonator and the second port,

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

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

Step 4.1, obtains channel power values;

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

Wherein, calculate energy loss by formula PL=P (T)-P (R), wherein, P (T) is energy value when sending data, and P (R) is the energy value receiving data; The PL calculated is substituted into following formula 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, the device parameter values of adjustment Some Second Order Elliptic function filter.

Preferably, described step 1 specifically comprises: the width w according to following formulae discovery 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, Z ₀=50 Ω, it is the characteristic impedance of the transmission line in the Sub-1G radio-frequency (RF) front-end circuit expected, for the wave impedance of free space, h is the thickness of pcb board, ε _effthe effective dielectric constant provided by following computing formula:

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

Preferably, described step 2 specifically comprises:

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 k ₁₂... k _{n-1, n}, wherein, wherein n=3;

Step 2.3, calculating filter coupling coefficient K ₁₂... K _{n-1, n}, wherein, n=3, wherein, Δ f is bandwidth, f ₀centered 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:

Step 2.6, according to the value C of the resonant capacitance (C1, C2) of following formulae discovery resonator _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, according to the value of each coupling capacitor of following formulae discovery (C3, C4, C5), actual is the value calculating (C3, C4) or (C4, C5):

C ₁₂＝K ₁₂C _resonator，C _n-1,n＝K _n-1,nC _resonator，n＝3；

When actual design elliptic function filter, generally 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 register of microcontroller and the energy value read being converted to signal strength signal intensity, channel power values is obtained.

Preferably, the device parameter values of the adjustment Some Second Order Elliptic function filter described in step 4.3 comprises further: first adjusting with 0.2NH is the value that adjustment step-length adjusts resonant inductance L1 or L2, then with the value of 0.3PF or 0.4PF for adjustment step-length adjustment coupling capacitance C3 or C5.

Sub-1G radio-frequency (RF) front-end circuit stability and the reliability of the present invention's design are high, and can based on RF energy measuring, device parameter values in adjustment Some Second Order Elliptic function low pass filter, reached impedance and the radio frequency source matches impedances of transmission line and load by the actual electronic element value changed in radio circuit, achieve the transmission of maximum transmission power.

Accompanying drawing explanation

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

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

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

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

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

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

Embodiment

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

RF front-end circuit is connected with antenna.Antenna is the important electronic unit of one of wireless device transceiving electromagnetic ripple signal.No matter be the communication engineering systems such as radio communication, broadcast, TV, radar, navigation, electronic countermeasures, remote sensing, every electromagnetic wave that utilizes carrys out transmission of information, and antenna all will be relied on to carry out work.Therefore, radio-frequency antenna is also most important for radio node communication, and the quality of Antenna Design will be directly connected to wireless signal tranception-quality, affect the reception and transmission range of wireless signal.

Antenna common in the market mainly contains PCB antenna, Chip antenna and Whip antenna.Wherein, PCB antenna cost is lower, but design difficulty is comparatively large, needs the less radio-frequency many factors considered; Chip antenna, i.e. ceramic antenna, volume is little, moderate cost, is suitable for the application scenarios compared with short haul connection; Whip antenna performance is best, and wireless signal amplification effect is obvious, and cost is relatively high.

Consider the factors such as the stable and cost of signal gain, impedance matching, channel width, node size, communication, the present invention preferably selects the Whip antenna meeting SMA (SubMiniature Version A) standard interface as the radio-frequency antenna of SD-WSN radio node, to adapt to the needs of different application scenarioss, but PCB antenna and Chip antenna are suitable for the present invention equally.

Sub-1G radio circuit of the present invention have employed KW01 radio frequency chip, because KW01 radio frequency chip inside is integrated with the rf receiver and transmitter SX1233 worked under Sub-1GHz radio band, compare other ZigBee radio frequency chips that Freescale company had previously released, its wireless receiving and dispatching is apart from farther.Simultaneously, in view of its inside is integrated with two-way cascade, unidirectional power amplifier, low noise amplifier, so when designing the radio-frequency (RF) front-end circuit of radio node, extend out power amplifier and low noise amplifier to strengthen the gain of wireless signal to increase the design of wireless transmission distance without the need to considering to adopt.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, for user's high-power wireless transmits the mode that provides more choices.

In addition, antenna can be divided into single ended antenna and differential antennae again.Single ended antenna is also called unbalanced antennas, and differential antennae is also called balancing antenna.KW01 radio frequency chip is different from the differential antennae that the ZigBee radio frequency chip of MC1321X, MC1322X and MC1323X series released before Freescale company uses, and what KW01 adopted is single ended antenna interface.Therefore, do not need to use Ba Lun (balance/imbalance transformer) circuit to carry out positive and negative change in voltage.This will simplify the hardware designs of Sub-1G less radio-frequency front-end circuit in SD-WSN radio node, reduces the design complexities of RF hardware, shortens the chip application development cycle.Wherein, single ended antenna mainly rely on (ground) as with reference to signal, its characteristic impedance is generally 50 Ω.

Fig. 1 shows the module map of Sub-1G radio-frequency (RF) front-end circuit.According to the design principle of embedded system hardware componentization, and consider multiple radio circuit design considerations such as signal gain, characteristic impedance coupling, low-pass filtering, signal reflex and radiation patterns, the present invention adopts Some Second Order Elliptic function low pass filter to combine the patten's design radio-frequency (RF) front-end circuit of two L shape matching network, gives the module map of Sub-1G radio-frequency (RF) front-end circuit as shown in Figure 1.Except the module shown in Fig. 1, Sub-1G radio-frequency (RF) front-end circuit also comprises the modules such as radio frequency chip, Some Second Order Elliptic function low pass filter and two L shape matching networks, wherein, Some Second Order Elliptic function low pass filter is connected with radio frequency chip, and it is mainly used in doing the characteristic frequency in high-frequency signal or the frequency component in frequency range strengthening or attenuation processing; Two L shape matching network is arranged between radio-frequency antenna and transmitting-receiving multiplexing pins RFIO and high-power transmitting terminal pin PA_BOOST, to provide rational characteristic impedance coupling, stopband to suppress, reduces the power loss on transmission line, improves transmit power capacity.Annexation between each device above-mentioned is known for a person skilled in the art, and main purpose of the present invention is design to Some Second Order Elliptic function low pass filter and two L shape matching network and parameter adjustment aspect, therefore, in order to the object simply clearly illustrated, the original papers such as radio frequency chip, Some Second Order Elliptic function low pass filter and two L shape matching networks are not shown in Fig. 1 particularly.

Sub-1G radio-frequency (RF) front-end circuit shown in Fig. 1, by software merit rating, can realize the switching of two kinds of wireless receiving and dispatching mode of operations.Wherein, first frequency selection circuit 13 is connected with the first antenna 11 by the electric capacity of 10pF, second frequency selection circuit 14 is connected with the first antenna 12 by the electric capacity of 10pF, and the first frequency selection circuit 13 and the second frequency selection circuit 14 are mainly used in carrying out frequency-selecting to useful signal, export glitch-free signal.After VR_PA (RF) pin blocks passive network 15 and the second AC blocking-up passive network 16 by the first AC, for the power amplifier PA of transmitting terminal provides pulsation-free pure power supply.When being in calibration power output mode, KW01 chip carries out the transmitting-receiving of wireless signal mainly through RFIO pin.In this mode, can provide the power stage in-18dBm to+13dBm scope, by software merit rating, the increment that minimum power regulates is 1dB.When being in enhancing power mode output, RFIO pin is used as signal receiving end, and PA_BOOST pin is used as high-power signal transmitting terminal, and by programmed configurations, changeable PA_BOOST end is two-way cascade or unidirectional emission power enhancement mode.Under enhancing power mode output ,-18dbm can be provided to export to+17dBm scope internal power.

Emphasis of the present invention is just design Sub-1G radio-frequency (RF) front-end circuit, and adjusts based on the parameter of RF energy measuring to circuit.To be described in detail it below.

A kind of design of the Sub-1G radio-frequency (RF) front-end circuit based on RF energy measuring proposed by the invention and parameter regulation means, mainly comprise the following steps:

Step 1, calculates the width of the transfer wire in Sub-1G radio-frequency (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 superfrequency (UHF), and its wavelength is generally linear module with cm.So, in radio circuit, when radio wavelength and the geometric size of discrete electronic component and the deposited copper conductor length of PCB comparable time, the characteristic impedance of transmission line can be produced, increase the radiation loss of circuit, reduce the transmitting power output of radio frequency source.Therefore, when drawing the PCB figure of radio-frequency (RF) front-end circuit, the trace width that choose reasonable applies copper conductor will change the characteristic impedance of transmission line, when the characteristic impedance of itself and radio frequency source matches time, can effectively reduce transmitting power loss, thus improve the reception and transmission range of radio node.

According to the approximate representation formula of characteristic of semiconductor impedance, simultaneously in conjunction with kirchhoffs law theoretical formula, as first approximation, suppose that compared with the thickness h of pcb board the thickness t of circuit can ignore, in this case, we can utilize and circuit relative dimensions (w and h) and DIELECTRIC CONSTANT ε _rrelevant empirical equation, can obtain the characteristic impedance Z of the transfer wire in general PCB ₀for:

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

Wherein, for the wave impedance of free space, w is the width of transfer wire, and h is the thickness of pcb board, ε _effthe effective dielectric constant provided 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 of general radio frequency chip inside is that 50 Ω or 200 Ω (can select, generally we select 50 Ω), in order to match with the characteristic impedance of radio frequency source, we expect that the transmission line in radio circuit needs the characteristic impedance Z had ₀also be 50 Ω (definite value), therefore actual DIELECTRIC CONSTANT ε that can be corresponding according to selected pcb board material type _r(by pcb board material, provider determined, general is also definite value), thickness h (adjustable value) and wireless frequency (definite value, the present invention is directed to 433MHz wireless frequency), simultaneously in conjunction with the law curve between transfer wire width w and PCB Thickness Ratio w/h, the design width w of required transmission line can be tried to achieve, thus reduce the wire transmission power loss of radio system.

The parameter that the impedance (50 Ω) that table 1-1 lists some typical PCB controls:

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

Step 2, design 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 being done and to strengthen or attenuation processing is very important, therefore, designing suitable filter most important.

According to Basis Theory of Circuit, filter can be divided into low pass, high pass, band to lead to and the large class of band stop filter four.For the variety classes of filter, the following parameter characteristic of main consideration:

(1) RF insertion loss: in the ideal case, is inserted into the filter in radio circuit, should not introduce other power losss in its free transmission range.But, in actual applications, cannot eliminate filter intrinsic, power loss 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 _lthe power that filter exports to load, P _inbeing the input power that filter obtains from signal source, is from the reflection coefficient of filter to signal source.

(2) return loss: be also called reflection loss.In high-frequency circuit, reflect do not mate due to transmission line impedance and produce incident wave energy reflection ratio.

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

(4) bandwidth: define filter and correspond to the upper side frequency of 3dB attenuation and the frequency-splitting of lower side frequency in passband:

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 the steep of filter response curve change near cut-off frequency:

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

(6) stopband suppresses: in the ideal case, all wish that filter has infinitely-great attenuation in stopband frequency range.But, in the design of actual radio frequency circuit, generally can only obtain the limited attenuation relevant to filter element number.In actual applications, suppress to set up with squareness factor to make stopband to contact, the Reference Design value usually suppressed using 60dB as stopband.

Fully with reference to three kinds of filter attenuation coefficients with under the prerequisite of the graph of relation of wireless frequency, in conjunction with the radiofrequency characteristics of KW01 chip rf receiver and transmitter SX1233, at the design part employing elliptic function low pass filter of radio frequency front-end circuit.Fig. 2 a compared for the attenuation change curve of elliptic function, binomial (Butterworth) and chebyshev low-pass filter.Wherein, Butterworth filter has dull attenuation curve, realizes in actual design than being easier to, but wants between passband and stopband, realize precipitous transkit attenuation change, then need more discrete electronic component, this can increase cost of hardware design; Chebyshev filter can obtain good abrupt transition attenuation curve, and 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 filter, the transition change of elliptic function filter between passband and stopband is the most precipitous, and shortcoming is that it has ripple effects at two ends.

In order to reduce radio frequency peripheral cell quantity as much as possible, reducing transmission line loss, and making the cut-off frequency characteristic that filter keeps good, the present invention adopts Some Second Order Elliptic function low pass filter as shown in Figure 2 b when designing radio-frequency (RF) front-end circuit.As shown in Figure 2 b, Some Second Order Elliptic function low pass filter of the present invention is by 2 resonant inductances, 2 resonant capacitances and 3 coupling capacitance compositions, wherein, first resonant inductance (L1) and the first resonant capacitance (C1) parallel connection form a LC parallel resonator, second resonant inductance (L2) and the second resonant capacitance (C2) parallel connection form the 2nd LC parallel resonator, by the first coupling capacitance (C3) ground connection between one LC parallel resonator and the first port, by the second coupling capacitance (C4) ground connection between one LC parallel resonator and the 2nd LC parallel resonator, by the 3rd coupling capacitance (C5) ground connection between 2nd LC parallel resonator and the second port.

Because elliptic filter transfer function is a kind of more complicated approximating function, utilize traditional method for designing carry out circuit network comprehensively analyze need carry out comparatively loaded down with trivial details mathematical computations.Therefore the present invention utilizes computation of table lookup method, consult each normalized value in the elliptic function low pass filter model of second order 0.1dB ripple, and calculate normalized coupling coefficient and filter coupled coefficient respectively according to required wireless signal centre frequency and bandwidth, thus select suitable resonant inductance value.Then, calculate each capacitance (comprising resonant capacitance and coupling capacitance) successively and convert in conjunction with the characteristic impedance value of front network port, finally obtaining calculated value.

The specific design step of each electronic element value in Some Second Order Elliptic function low-pass filter circuit as shown in Figure 3.Shown in composition graphs 3, step 2 specifically comprises 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.

The each element normalized value of elliptic function filter when relief volume is 0.1dB in table 1-2 band

When designing elliptic function filter, the target that first will clearly design, supposes that we need design centre frequency f ₀the Some Second Order Elliptic function filter that bamboo is 433MHz, bandwidth If is 2MHz (± 1MHz), characteristic impedance is 50 Ω.As the first step of design, first will to show in 1-2 stop-band frequency for the normalized component value under 2MHz is as foundation, try to achieve one group of identical parameter required with design, Some Second Order Elliptic function filter should have 3 parameters, makes it be g1, g2 and g3 (gn is the parameter of n-1 rank high pass filter).The value of this g1, g2 and g3 just equals normalized component value (C3, C1 and L1 respectively in corresponding diagram 2b).

Step 2.2, calculates normalized coupling coefficient k ₁₂... k _{n-1, n,}wherein, wherein n=3;

In step 2.2, Some Second Order Elliptic function filter is made up of 2 resonators (resonator that C1 and L1, C2 and L2 in Fig. 2 b form) and 3 coupler k (C3, C4 and C5), we obtain one group of normalized coupling coefficient k12 according to g1, g2 and g3, k23.

Step 2.3, calculating filter coupling coefficient K ₁₂... K _{n-1, n}, wherein, n=3, wherein, Δ f is bandwidth, f ₀centered by frequency;

In step 2.3, Some Second Order Elliptic function filter is made up of 2 resonators (resonator that C1 and L1, C2 and L2 in Fig. 2 b form) and 3 coupler k (C3, C4 and C5), we obtain one group of normalized coupling coefficient k12 according to g1, g2 and g3, 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, be generally about 10nH, there is no absolute requirement, the present invention preferably adopts 6.8nH, L1 and the L2 namely 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:

Step 2.6, the value according to the resonant capacitance (C1, C2) of following formulae discovery 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 _resonatorbe resonant capacitance value (that is, the value of the first resonant capacitance (C1) and the second resonant capacitance (C2)), in the present invention, the first resonant capacitance (C1) is identical with the value of the second resonant capacitance (C2).

Step 2.7, according to each coupling capacitor values of following formulae discovery:

C ₁₂＝K ₁₂C _resonator，C _n-1,n＝K _n-1,nC _resonator，n＝3。

Because comprising two coupling coefficient K12 and K23 in circuit, but these two coupling coefficients as coupling element for realizing coupling filter, so will realize filter, can not must change coupling capacitor into K12 and K23, 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 above, in its Fig. 2 b, the impedance of two ends Port is respectively Z1 and Z2, be not 50 desired Ω, so we also need to be become desired value, carrying out impedance transformation is exactly the ratio K of first trying to achieve these two characteristic impedances, then remove each capacitance in Fig. 2 b with K, go to take advantage of each inductance value in Fig. 2 b circuit with K.

So far, we just obtain impedance is all electric capacity, inductance value in elliptic function filter circuit under 50 Ω, also just completes the design of Some Second Order Elliptic function low pass filter.

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

Figure 4 shows that the simple L-type matching network be made up of electric capacity and inductance two discrete electronic components designs a model, wherein, Z _tfor wireless signal is in the output impedance of present frequency point, Z _afor the input impedance of antenna, Z _mbe then the output impedance of L shape matching network.In order to realize maximum power transfer between radio signal source and load, needing to make the output impedance of signal source equal with load impedance conjugation, being Z _mwith Z _aconjugate complex number is equal.Therefore, impedance Z _mvalue equal Z _tconnect with inductance L again with after electric capacity C parallel connection:

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

Wherein, B _c=wC is the susceptance of electric capacity, X _l=wL is the induction reactance of inductance.The impedance of transmitting set and antenna is expressed 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:

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

The real part of (3.7 formula) and imaginary part are separated, then can obtain 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 value in radical sign on the occasion of and be greater than for ensure (1.9a) formula be on the occasion of, choosing this formula is positive sign.(1.9a) formula is substituted into (1.8a) formula and can obtain X _lfor:

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

By the parameter in actual design radio circuit process, comprise the output impedance Z of signal at present frequency point _twith the input impedance Z of antenna _a, (1.9a) and (1.9b) formula of substitution can draw, the approximated reference design load of electric capacity and inductance in L-type matching network.

Some Second Order Elliptic function low pass filter and the combination of two L shape matching network, mainly contain following characteristics:

(1) between radio-frequency antenna and transmitting-receiving multiplexing pins RFIO and high-power transmitting terminal pin PA_BOOST, provide rational characteristic impedance coupling, stopband to suppress, reduce the power loss on transmission line, improve transmit power capacity.

(2) in L shape match circuit, by using the value of suitable electric capacity and inductance to carry out impedance transformation, guaranteeing to form minimal reflection between emission source and load, realizing the optimization of transmitting power.

(3) the Some Second Order Elliptic function low pass filter design scheme adopting required element amount less, while the design complexities reducing radio circuit, effectively improves stability and the reliability of system.

By above description, designed the circuit of Some Second Order Elliptic function low-pass filter circuit in Sub-1G radio-frequency (RF) front-end circuit and L-type matching network, but the device parameter values in circuit is theory to be calculated, actual effect is undesirable greatly.The present invention is based on energy detection algorithm to infer the actual value of each electronic element value of Sub-1G front end circuit design median filter.According to the transmit signal strength of transmitting node, energy measuring obtains node received energy value, utilize theoretical and experience to obtain quality of connection and calculate reflection coefficient in the design of Sub-1G radio-frequency (RF) front-end circuit and return loss radio-frequency performance parameter, and reach impedance and the radio frequency source matches impedances of transmission line and load by changing actual electronic element value in radio circuit, realize the transmission of maximum transmission power.

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

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

Step 4.1, obtains channel energy;

Because the inner integrated SX1233 wireless transceiver of used Sub-1G chip-KW01 can support the physical layer service functions such as the instruction of channel energy detection, link-quality, clear channel assessment (CCA), so KW01 has the hardware implementing of detected energy, therefore the energy measuring of wireless signal, can pass through hardware implementing.The signal energy value obtained can be deposited into RssiValue [7:0] the energy value field of the RegRssiValue register of microcontroller by hardware by certain calculating conversion.Conversion in signal strength signal intensity and register between RssiValue [7:0] can by being converted to, namely

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 the energy loss of wireless signal on transmission line and internodal communication distance;

Because the value of the register RssiValue [7:0] by reading Sub-1G chip-KW01, and through type (2) can calculate the wireless data signal strength signal intensity herein received.Due to the energy P (T) during known transmission data and receive data energy value P (R) (these two value sizes known, can be regulated by the MCU side software merit rating of KW01 chip), therefore can show that transmission range is for actual energy loss when D between with fixing node.

PL＝P(T)-P(R) (3)

Binding isotherm propagation loss formula LFS=32.44+20*LOG (D) KM+20*LOG (F) MHZ simultaneously, by analyzing, between actual energy loss PL and theoretical Propagation of Energy loss LFS, there is linear equivalence relation, therefore can PL=LFS be drawn, namely

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, known quantity are substituted into formula (4) and can draw communication distance D.Be more than the theoretical foundation of the spacing calculating 433MHZ channel two nodes and be under ideal conditions.But when reality is tested, owing to being subject to the impact of the factors such as other electromagnetic waves, barrier, humidity, temperature, cause 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 and internodal communication distance, the device parameter values of adjustment Some Second Order Elliptic function filter.

As previously mentioned, due to utilize traditional method for designing carry out circuit network comprehensively analyze need carry out comparatively loaded down with trivial details mathematical computations, therefore the general computation of table lookup method when designing, consult each normalized value in low-pass filter function model, and calculate normalized coupling coefficient and filter coupled coefficient respectively according to centre frequency and bandwidth, thus select suitably resonant inductance value.Then, calculate resonant capacitance and each coupling capacitance successively and characteristic impedance value in conjunction with front network port converts, finally obtain calculated value.

Simultaneously, the present invention is optimized according to the above-mentioned calculated value radio frequency circuit to energy loss, reasonably select the component value of capacitor and inductor in Transformation Graphs 2b, during adjustment, should with C3, L1 or C5, L2 is main adjustment aim, first adjust the value of inductance L 1 or L2, and be that adjustment step-length carries out left and right adjustment test with 0.2NH, when select inductance value make the transmission and reception energy value of radio node reach one be relatively better worth time, adjust C3 or C5 again, during adjustment electric capacity, with 0.3PF or 0.4PF for adjustment step-length, find the maximum performance point of filter, realize the transmission of maximum transmission power as much as possible, impedance and the radio frequency source matches impedances of semiconductor circuits and load must be made.

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

Table 1-3Sub-1G radio-frequency (RF) front-end circuit experiment parameter illustrates (for 433MHz)

The present invention need not strengthen antenna, carrying out parameter adjustment, can reach the communication distance of 1000 meters by measuring energy, and table 1-4 illustrates when 700 meters with 1000 meters of distances, the packet loss contrast of wireless data transceiving under different transmitting powers.As can be seen from the table, after circuit element parameter adjustment, wireless data transceiving effect is significantly improved.

Data packet transceive test result contrast before and after parameter adjustment under table 1-4433MHz

Above content is only preferred embodiment of the present invention, and for those of ordinary skill in the art, according to thought of the present invention, all will change in specific embodiments and applications, this description should not be construed as limitation of the present invention.

Claims (7)

1., based on the design of Sub-1G radio-frequency (RF) front-end circuit and the parameter regulation means of RF energy measuring, described method specifically comprises the following steps:

Step 1, calculates the width of the transfer wire in Sub-1G radio-frequency (RF) front-end circuit;

Step 2, design Some Second Order Elliptic function low pass filter, described Some Second Order Elliptic function low pass filter is by 2 resonant inductances, 2 resonant capacitances and 3 coupling capacitance compositions, wherein, first resonant inductance (L1) and the first resonant capacitance (C1) parallel connection form a LC parallel resonator, second resonant inductance (L2) and the second resonant capacitance (C2) parallel connection form the 2nd LC parallel resonator, by the first coupling capacitance (C3) ground connection between one LC parallel resonator and the first port, by the second coupling capacitance (C4) ground connection between one LC parallel resonator and the 2nd LC parallel resonator, by the 3rd coupling capacitance (C5) ground connection between 2nd LC parallel resonator and the second port,

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

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

Step 4.1, obtains channel power values;

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

Wherein, calculate energy loss by formula PL=P (T)-P (R), wherein, P (T) is energy value when sending data, and P (R) is the energy value receiving data; The PL calculated is substituted into following formula 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, the device parameter values of adjustment Some Second Order Elliptic function filter.

2. the design of the Sub-1G radio-frequency (RF) front-end circuit based on RF energy measuring according to claim 1 and parameter regulation means, it is characterized in that, described step 1 specifically comprises: the width w according to following formulae discovery 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, Z ₀=50 Ω, it is the characteristic impedance of the transmission line in the Sub-1G radio-frequency (RF) front-end circuit expected, for the wave impedance of free space, h is the thickness of pcb board, ε _effthe effective dielectric constant provided by following computing formula:

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

3. the design of the Sub-1G radio-frequency (RF) front-end circuit based on RF energy measuring according to claim 1 and parameter regulation means, it is characterized in that, described step 2 specifically comprises:

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 k ₁₂... k _{n-1, n}, wherein, wherein n=3;

Step 2.3, calculating filter coupling coefficient K ₁₂... K _{n-1, n}, wherein, n=3, wherein, △ f is bandwidth, f ₀centered 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, according to the value C of the resonant capacitance (C1, C2) of following formulae discovery resonator _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, the value according to each coupling capacitor of following formulae discovery (C3, C4, C5):

C ₁₂＝K ₁₂C _resonator，C _n-1,n＝K _n-1,nC _resonator，n＝3；

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

4. the design of the Sub-1G radio-frequency (RF) front-end circuit based on RF energy measuring according to claim 3 and parameter regulation means, it is characterized in that, in step 2.4, the resonant inductance value of selection is 6.8nH.

5. the design of the Sub-1G radio-frequency (RF) front-end circuit based on RF energy measuring according to claim 3 and parameter regulation means, it is characterized in that, in step 2.8, required characteristic impedance is 50 Ω.

6. the design of the Sub-1G radio-frequency (RF) front-end circuit based on RF energy measuring according to claim 1 and parameter regulation means, it is characterized in that, by reading the energy value field of the register of microcontroller and the energy value read being converted to signal strength signal intensity, obtain channel power values.

7. the design of the Sub-1G radio-frequency (RF) front-end circuit based on RF energy measuring according to claim 1 and parameter regulation means, it is characterized in that, the device parameter values of the adjustment Some Second Order Elliptic function filter described in step 4.3 comprises further: first adjusting with 0.2NH is the value that adjustment step-length adjusts resonant inductance L1 or L2, then with the value of 0.3PF or 0.4PF for adjustment step-length adjustment coupling capacitance C3 or C5.