CN101183878B - Low-power consumption wireless receiver radio frequency front end circuit - Google Patents

Abstract

The invention relates to a low power consumption RF front-end circuit of the wireless receiver, belonging to the technical field of the integrated circuit of the RF wireless receiver, , comprising an RF input matching network, an amplifier stage, a bridge transformer, an LO switch stage, an IF load and a current source bias circuit; wherein, the RF input matching network implements the impedance matching between an antenna and the amplifier stage; the amplifier stage is used for amplifying the signal, the bridge transformer transfers the signal amplified to the LO switch stage and implements DC isolation between the front stage and back stage; the LO switch stage is used for implementing frequency mixing of the RF current signal and the LO signal and outputting alternatively the IF signal on an outputting differential load. Compared with the traditional RF front-end circuit, the circuit structure can use an on-chip integrated transformer or an on-chip inductor to implement inputting matching, and use the on-chip integrated transformer to implement the amplifying and downward frequency mixing of the RF signals perfectly, which simplifies the circuit structure. The circuit can be used in a low power supply voltage environment, and has the advantages of low DC power consumption, and less circuit noise and signal distortion.

Description

A kind of low-power consumption wireless receiver radio frequency front end circuit

Technical field

The invention belongs to wireless radiofrequency receiver ic technical field, be specifically related to a kind of RF front-end circuit in the wireless receiver integrated circuit (RF Front-end) that is applied to.The video receiver chip that can be used for broadband wireless network and high speed wireless data transmission techniques standard is like WiMax and UWB etc.

Background technology

Along with communication and development of semiconductor; Various GSMs and wireless data transmission technology develop rapidly; Representative in them has GSM, CDMA and Bluetooth and WiFi etc.; Particularly high-data-rate wireless transmission technologys such as 3G, IEEE802.11a/b/g, WiMax and UWB super-broadband tech continue to bring out in recent years, and high performance video receiver has been proposed very high requirement.Because the carrier frequency of mobile communication and wireless data transmission technology is higher, the signal bandwidth that adopts in the part technology is very big, and the less radio-frequency receiver receives and amplifies the wireless signal amplification that is in high-frequency very or the very big bandwidth digitized signal processing of going forward side by side.Simultaneously, the mobile communication or the wireless technology overwhelming majority are applied on the handheld terminal, and this just requires the signal of handheld terminal to receive and transmitter must reduce power consumption as far as possible to lengthen working hours.

Radio-frequency front-end is as one of chief component in the wireless communication receiver, and its effect is exactly the frequency translation that the small-signal that antenna receives is amplified and carried out signal.Generally these two functions are distributed to low noise amplifier (Low Noise Amplifier) respectively in the conventional radio frequency front-end circuit and down-conversion mixer (Down Conversion Mixer) two parts are separate.The shortcoming of doing like this is that two parts circuit interacts, need experience during design independent design, emulation to interconnect, the flow process of associative simulation, parameter modification, design difficulty and cycle strengthen.The difficulty of two parts circuit interface design causes the performances such as power consumption, noise and the linearity of integrated circuit not optimized fully.

The radio frequency input matching network of tradition broadband rf front end circuit generally is made up of with input common source transistor and source inductance the filter network of grid on-chip inductor, electric capacity and combination thereof jointly, and the on-chip inductor number of use is more, and chip occupying area is bigger.

Summary of the invention

The purpose of this invention is to provide a kind of RF front-end circuit that is used for the wireless radiofrequency receiver, requiring its operating frequency range characteristic is broadband and ultra broadband, and dc power is little, supply voltage is low, and the linearity of little while of noise factor is high.

RF front-end circuit provided by the invention, its structure is as shown in Figure 1, and this RF front-end circuit comprises that input matching network, amplifying stage, bridging transformer and LO switching stage and the load of IF intermediate frequency and current source biasing fund-raising circuit connect to form; Wherein the radio frequency input matching network is done the impedance matching between antenna and the amplifying stage; Amplifying stage carries out the amplification of signal; Signal after bridging transformer will amplify passes to the LO switching stage and realizes the dc-isolation of front and back level, and the LO switching stage makes RF current signal and LO signal carry out mixing and on the output differential load, alternately exports the medium-frequency IF signal.

Among the present invention, the radio frequency input matching network can be realized by the feedback arrangement that integrated transformer on integrated transformer on the sheet or the sheet combines with the amplifying stage subelement to form.Spendable on-chip transformer architecture with the classification like Fig. 2 (a), (b), (c), (d), (e), (f) shown in.Fig. 3 provides the monolateral circuit diagram of two kinds of modular designs; A kind of elementary input of integrated transformer from the sheet that is radio frequency rf signal; Again by secondary homophase termination amplifying stage master amplifier tube grid; The source electrode of main amplifier tube connects feedback inductance, and drain electrode connects back level load circuit, and other port of transformer all connects and exchanges ground (fixed bias voltage, the drain electrode of difference common mode current offset or ground); Another kind is that radio frequency rf signal is imported from the elementary end of on-chip transformer, another termination amplifying stage master amplifier tube grid, and amplifying stage master amplifier tube source electrode connects the transformer secondary output end of oppisite phase, and secondary another termination exchanges ground, and main amplifier tube drain electrode connects back grade amplifying circuit.

Among the present invention, amplifying stage is generally MOS FET transistor or the combination of bipolar triode that common source connects method or cascade connected mode, and can become feedback arrangement with the input matching network combination of elements.With the cascade is example, and common source Guan Weizhu amplifier tube is in order to provide bigger mutual conductance; Bank tube can provide bigger output impedance for auxiliary amplifier tube altogether, and the isolation of back level with the RF input is provided, and avoids the reverse leakage of LO large-signal.

Among the present invention, bridging transformer is an integrated transformer on the sheet, its structure with the classification like Fig. 2 (a), (b), (c), (d), (e), (f) shown in.Said bridging transformer is an integrated transformer on the sheet; Its effect is to be coupled to secondaryly from elementary the radiofrequency signal of amplifying, and offers the LO switching stage and carries out mixing.If amplifying stage is that single-ended structure, LO switching stage are single balanced structure, its method of attachment is shown in Fig. 4 (a); Be two balanced structures if amplifying stage is single-ended structure, LO switching stage, its method of attachment is shown in Fig. 4 (b); Be two balanced structures if amplifying stage is differential configuration, LO switching stage, its method of attachment is shown in Fig. 4 (c).On-chip transformer wherein can provide bias voltage or bias current from the coil centre tap.

Among the present invention, the LO switching stage is generally NMOS FET transistor or NPN bipolar triode, and radiofrequency signal generally from the input of its common source (penetrating) end, import from grid (base) utmost point by the LO signal.

The intermediate frequency load is generally resistance on the sheet, electric capacity, inductance or their combinational network, the circuit that can be used for broadband down-conversion, arrowband down-conversion and up-conversion and special intermediate frequency frequency response requirement is arranged.Its current source load is fixing NMOS pipe or a NPN triode of grid (base stage) voltage.

This circuit can adopt single-ended structure or fully differential structure, and technologies such as available CMOS, BiCMOS, Bipolar realize.

Go up integrated transformer for said and totally be divided into two kinds; Plane (planar) and cascade type (stacked); And according to the cross modal of primary and secondary coil; Plane be divided into tapped (tapped) and staggered form (interleaved) again, cascade type be divided into complete eclipsed form and dislocation eclipsed form again.Coupling ratio is loose between the flat surface transformer coil, and wherein tapped flat surface transformer coupling coefficient is minimum, is about 0.3 ~ 0.5; The staggered form flat surface transformer is according to the spacing size of primary and secondary coil, and the coupling coefficient scope is about 0.7 ~ 0.8; And the cascade type transformer is overlapping closely owing to upper/lower layer metallic, and coupling coefficient can reach more than 0.9.Plane type transformer only utilizes top-level metallic, and the top-level metallic of technology is thicker usually, and resistivity is low; And parasitic capacitance is little, the Q value of transformer coil and self-oscillation frequency are improved, and stacked parasitic capacitance and series resistance is all bigger; The Q value is not high, needs careful use.

Integrated transformer also can come out from the centre tap of primary and secondary coil on the sheet; Make primary and secondary all become three terminal device, centre tap can connect interchange ground (supply voltage, decoupling capacitance or ground) and be used for forming the transformer of difference input and output and direct voltage can be provided or interchange ground.

This circuit is if realize with BiCMOS or Bipolar technology, then Fig. 3, transistor shown in 5 is all replaceable is triode, annexation and signal are constant.

The design's outstanding improvements have two.

First improvements use on-chip transformer according to the input matching network that is connected to form shown in Figure 3, realize Broadband Matching.With Fig. 3 (b) is example, and its small-signal input equivalent network is as shown in Figure 6.Consider chip bonding line inductance L _BWAnd parasitic capacitance C _Par, its input impedance can be written as:

$Z_{\mathrm{in}}=L_{\mathrm{BW}}s+\frac{(1+\mathrm{nk})L_{S}s+(1+B)r_S+r_{\mathrm{se}}+\frac{1}{C_{\mathrm{gs}}S}}{1-\frac{k}{n}(1+B)},---\left(1\right)$

Wherein $B=\frac{g_m}{C_{\mathrm{Gs}}S}=-j\frac{{\mathrm{\ω}}_T}{\mathrm{\ω}}$ , and L _SBe self inductance of transformer secondary output coil, r _SBe the dead resistance of transformer secondary output coil, r _SeBe the dead resistance of transformer, L _BWBe bonding line stray inductance, C _ParBe the parasitic capacitance of chip PAD and cabling, ω _TBe the cut-off frequency of main amplifier tube, ω is the input signal angular frequency, C _GsBe main amplifier tube grid source overlap capacitance, k is transformer coupled coefficient, and n is the transformer coil turn ratio.

It is thus clear that: if will make input impedance matching to 50 ohm, at first need confirm and the relevant ω of main amplifier tube direct current _T, secondly need to confirm main amplifier tube size, transformer turn ratio and coupling coefficient, with the suitable on-chip transformer of design parameter.According to (2), (3) formula, when parameter selects to make the enough little and real part of input impedance imaginary part near 50 ohm, can think that reaching input matees.

Weigh the broadband character of input coupling; As long as calculate the Q value of input impedance, i.e.

.When design parameter is suitable, can make that the Q value is less, the Broadband Matching effect improves.

This design needs independent grid inductance and source feedback inductance to merge into transformer script, can improve integrated level, reduce chip area, and the Broadband Matching effect does not change.

Second outstanding improvements is with the elementary laod network as the RF amplifying stage of on-chip transformer, replaces the inductance ohmic load network of traditional LNA, replaces the RF of traditional Gilbert frequency mixer to import the mutual conductance pipe with on-chip transformer, and be as shown in Figure 7.

The equivalent inductance of transformer and parasitic series resistance and add the load that parallel resistance is formed amplifying stage jointly, its effect is identical with the laod network of LNA.

And import the mutual conductance pipe with the RF of transformer replacement frequency mixer, its advantage is described below:

Analysis conventional Gilbert frequency mixer RF mutual conductance pipe is an example with the NMOS pipe, and its effect is the small-signal current that the small signal of grid is converted to drain electrode, and the current-voltage gain of conversion is that the mutual conductance of NMOS pipe self is:

$g_m=\sqrt{\frac{2I}{{\mathrm{\μ}}_0{C}_{\mathrm{OX}}\frac{W}{L}}}---\left(4\right)$

Wherein I is the quiescent current that flows through pipe, μ ₀Be the carrier mobility of pipe, C _OXBe unit grid oxygen electric capacity, W and L are respectively the wide of pipe and long.

The on-chip transformer that the design adopted can through electromagnetic coupling effect, be coupled to secondary coil with institute's radio frequency rf signal (voltage or electric current) in addition on the primary coil.If the elementary and secondary coil turn ratio of transformer is n (turnsratio), coupling coefficient is k (coupling factor), and their expression formula is following,

$n=\sqrt{\frac{L_S}{L_P}}---\left(5\right)$

$k=\frac{M}{\sqrt{L_P{L}_S}}---\left(6\right)$

L wherein _PAnd L _SBe respectively self inductance value of primary coil (primary) and secondary coil (secondary), M is two mutual inductance values between the coil.Then it elementaryly to secondary electric current gain amplifier is:

$A_i=\frac{i_P}{i_S}=\mathrm{nk}---\left(7\right)$

Even its current gain is less than 1, because transformer input impedance is little, for certain input voltage signal, the electric current that flows through primary coil increases, and the mutual conductance of equivalence is close with the RF mutual conductance pipe of traditional Gilbert frequency mixer.

The RF mutual conductance pipe of tradition Gilbert mixer; Especially in sub-micron, deep submicron process; Self have multiple noises such as channel current noise, induced grid noise, low frequency flicker noise, the LO switching stage also can be introduced noise, makes that the noise of mixer is very big.And if adopt on-chip transformer to replace RF mutual conductance pipe; Because on-chip transformer is a passive device, does not introduce noise under the ideal situation, even the parasitic parameter of consideration own; Below the 10GHz frequency; Substrate eddy current effect and electric current skin effect are also not serious, and its parasitic resistance of connecting has only several ohms usually, and noise contribution will be very little also.

The RF mutual conductance pipe of tradition Gilbert mixer is handled the limited in one's ability of large-signal, promptly because it works in being limited in scope of linear amplification district, in case input signal is excessive, will cause transistor to get into the inelastic region, worsens the frequency mixer ability to work significantly.If adopt on-chip transformer, because it is a passive device, its linearity is very high under the ideal situation, even because the influence of parasitic parameter generally also can reach the linearity above normal transistor.

After using the RF mutual conductance pipe replacement of on-chip transformer with traditional Gilbert frequency mixer; Because impedance is very little under the on-chip transformer direct current situation; The direct current pressure drop is just very little, and like this from the entire circuit two-layer transistor (LO pipe and offset) that only superposeed, and traditional Gilbert circuit has three range upon range of adding (LO pipe, RF pipe and offset) to guarantee that same all pipes are under the situation in operate as normal district; Reduce the pressure drop of one deck pipe, make and select lower supply voltage to become possibility.

Equally; According to (4) (7) formula; Use the transadmittance gain of on-chip transformer structure only relevant with coupling coefficient k with turn ratio n; And the mutual conductance of traditional Gilbert frequency mixer RF tube current and bias current, pipe breadth length ratio are relevant, and the circuit of on-chip transformer structure only need guarantee to provide the bias current of LO switching stage operate as normal like this, and need not to provide the electric current of increase to make that the mutual conductance of RF pipe is enough big.In this case, adopt the design of on-chip transformer more to save electric current.。

In a word, use one (single-end circuit) or two on-chip transformers (fully differential), just realized acting on greatly, realized that the signal in broadband amplifies and following mixing as load of RF amplifying stage and frequency mixer transconductance stage two.

Description of drawings

Fig. 1 is the present invention's electrical block diagram.

Fig. 2 is an integrated transformer structural diagrams on the sheet.Wherein, (a) be the vertical view of integrated transformer (tappedplanar on-chip transformer) on the tap type planar chip; (b) be the cutaway view of integrated transformer (tapped planaron-chip transformer) on the tap type planar chip; (c) be the vertical view of integrated transformer on the chiasma type planar chip (interleaved planaron-chip transformer); (d) be the cutaway view of integrated transformer on the chiasma type planar chip (interleaved planaron-chip transformer); (e) vertical view of integrated transformer (stacked on-chiptransformer) on the range upon range of matrix, this example is complete eclipsed form, (f) cutaway view of integrated transformer (stacked on-chiptransformer) on the range upon range of matrix.

Fig. 3 is the connection layout of input matching network transformer.Wherein, (a) to connect input transformer elementary for input signal, and secondary main amplifier tube grid (base) utmost point that connects, the other end of primary and secondary all connect and exchange ground, the only inductance of main amplifier tube source (penetrating) utmost point order.(b) input signal connects the elementary end of input transformer, elementary another termination master amplifier tube grid (base) utmost point, and secondary anti-phase termination master amplifier tube source (penetrating) utmost point, another termination exchanges ground.

The connection layout of Fig. 4 bridging transformer and LO switching stage.Wherein, (a) amplifying stage is single-ended structure, LO switching stage when being single balanced structure, bridging transformer and the method for attachment of LO switching stage.When (b) amplifying stage is single-ended structure, LO switching stage for two balanced structure, bridging transformer and the method for attachment of LO switching stage.When (c) amplifying stage is differential configuration, LO switching stage for two balanced structure, bridging transformer and the method for attachment of LO switching stage.

Fig. 5 is the connection layout of LO switching stage.

Fig. 6 is the small-signal equivalent circuit of circuit connecting method shown in Fig. 3 (b).

Fig. 7 is the sketch map of the design's second outstanding improvement

Fig. 8 is the circuit diagram of the design's practical implementation instance.

Fig. 9 is the input coupling S11 parameters simulation figure of practical implementation example circuit.

Figure 10 is the conversion gain analogous diagram of practical implementation example circuit, and this figure only illustrates the simulation result of one of three frequency ranges, wherein the input rf signal frequency range be 3.6GHz to 4.2GHz, the LO signal frequency is 3.9GHz.

Figure 11 is the noise factor analogous diagram of practical implementation example circuit, and this figure only illustrates the simulation result of one of three frequency ranges, wherein the input rf signal frequency range be 3.6GHz to 4.2GHz, the LO signal frequency is 3.9GHz, the IF frequency deviation is that 1MHz is to 300MHz.

Figure 12 puts analogous diagram for the input of practical implementation example circuit with reference to third order intermodulation, and wherein the LO signal frequency is 3.9GHz, and the RF signal frequency is 4GHz and 4.001GHz.

Label among the figure: 1 is the outer layer metal winding, and 2 is the inner layer metal winding, and 3 is the medium of oxides layer between metal and the substrate, and 4 is silicon substrate, and 5 is bottom metal, and 6,7 is two metal winding that are coupled mutually, and 8,9 is two metal winding that overlap up and down.

Embodiment

This structure of radio-frequency front end is applied to 3.1GHz in the fully differential RF front-end circuit of 4.7GHz frequency range MB-OFDM UWB radio-frequency transmitter, and concrete design parameter is as shown in Figure 8.Adopt 0.18um RF CMOS 1P6M technology, emulation tool is Cadence SpectreRF, wherein V _B1=0.82V, V _B2=0.68V, the gate bias voltage of RF amplifying stage master amplifier tube M1/2 is 1.08V, the gate bias voltage of LO switching stage pipe is 0.8V.

The transformer that input matching network adopts is a tap type plane on-chip transformer, the layer 6 metal routing, and primary coil sense value is 3.5nH, and secondary coil sense value is 0.8nH, and turn ratio is 1: 0.48, and coupling coefficient is about 0.4; What bridging transformer adopted is chiasma type plane on-chip transformer, and layer 6 metal routing, primary and secondary coil all are 2n, and promptly turn ratio is 1: 1, and coupling coefficient is 0.8.

LO local oscillation signal frequency is respectively 3.432GHz, 3.960GHz, 4.488GHz, and the frequency range of RF input signal is about 3.1GHz to 4.7GHz, and IF intermediate-freuqncy signal frequency range is that 4.125MHz is to 264MHz.

Concrete simulation result such as following table:

	Front-end
				Index parameter	Simulation result (NOM Corner)
RF incoming frequency (GHz)	3.1~4.7
				Input coupling S11 (dB)	-9~-14
LO frequency/power	3.432GHz/0dBm	?4.488GHz/0dBm	?3.96GHz/0dBm
				IF(MHz)	4.125~264
Linearity IIP3 (dBm)	-4.3
				Gain (dB)	21.1~22.0	?22.0~22.7	?19.9~21.7
Noise factor (dB)	2.5	?2.5	?3.5
				Dc power	1.5V×12.5mA

Wherein the part simulation result can be referring to Figure of description 9 to Figure 12.

Claims (1)

1. low-power consumption wireless receiver radio frequency front end circuit; Be applied to 3.1GHz in the fully differential RF front-end circuit of 4.7GHz frequency range MB-OFDM UWB radio-frequency transmitter; It is characterized in that being connected successively and forming with the current source biasing circuit by radio frequency input matching network, amplifying stage, bridging transformer and switching stage and the load of IF intermediate frequency; Wherein, The radio frequency input matching network is done the impedance matching between antenna and the amplifying stage; Amplifying stage carries out the amplification of signal, and the signal after bridging transformer will amplify passes to switching stage and realizes the dc-isolation of front and back level, and switching stage makes RF current signal and switching stage signal carry out mixing and on the output differential load, alternately exports the medium-frequency IF signal;

Said radio frequency input matching network is realized by the feedback arrangement that integrated transformer on integrated transformer on the sheet or the sheet combines with the amplifying stage subelement to form; Wherein, Go up integrated transformer combines formation with the amplifying stage subelement feedback arrangement for said; Two kinds of ways of realization are arranged: a kind of elementary input of integrated transformer from the sheet that is radio frequency rf signal, by secondary homophase termination amplifying stage master amplifier tube grid, the source electrode of main amplifier tube connects feedback inductance again; Drain electrode connects back level load circuit, and other port of transformer all connects and exchanges ground; Another kind is that radio frequency rf signal is imported from the elementary end of on-chip transformer, another termination amplifying stage master amplifier tube grid, and amplifying stage master amplifier tube source electrode connects the transformer secondary output end of oppisite phase, and secondary another termination exchanges ground, and main amplifier tube drain electrode connects back grade amplifying circuit;

Said amplifying stage is that common source connects method perhaps connects method for cascade transistor combination, perhaps is the combination of bipolar triode;

Said switching stage is single balanced structure and two balanced structures, and even amplifying stage is a single-ended structure, and switching stage is single balanced structure or two balanced structure; If amplifying stage is a differential configuration, switching stage is two balanced structures.

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