JP2008505579A - Radio receiver front end and method for frequency conversion of input signal - Google Patents

Abstract

An N-phase radio receiver front end for converting an input signal having a first frequency into an output signal having a second frequency, and an input signal at the N-phase radio receiver front end for converting Method.
An input port of an N-phase radio receiver front end is directly connected to an input port of a low noise amplifier circuit (50). The mixer device (50a) is a current mode type mixer device. The output port of the low noise amplifier circuit is directly connected to the input port of the mixer device. A signal generator is operatively connected to the mixer device to generate an N phase shift local oscillator signal.

Description

  The present invention relates to an N-phase radio receiver front end for converting an input signal having a first frequency into an output signal having a second frequency. The invention also relates to a method for converting an input signal having a first frequency into an output signal having a second frequency.

  Conventional radio receiver front-end designs implement an incoming radio frequency (RF) signal that is converted to one or more intermediate frequencies that are subsequently converted to baseband. The radio receiver front end may include a low noise amplifier circuit (LNA) with sufficient voltage gain. Next to the low noise amplifier circuit, one or several mixers are provided to convert the input signal into an IF signal supplied at the output of the mixer.

  The quadrature radio receiver front-end mixes differential or single-ended input signals with four local oscillator signals of different phases, for a total of two, one for the I channel and one for the Q channel. Designed to obtain an output signal.

  The input signal may include superimposed out-of-band interference. In wireless receiver front ends known in the art, one or several filters are provided to process the input signal. A pre-filter such as a band selection filter is provided before the LNA to suppress out-of-band interference. A filter may be further added to process the input signal. To make the radio receiver front end cheap, it may be implemented as part of an integrated circuit. However, it is difficult to implement the filter with an on-chip design. Therefore, in many cases, the filter must be implemented off-chip. This is disadvantageous because off-chip components make the radio receiver front end more expensive, larger and more complex. As a result, most off-chip filters have been removed in the development of small and inexpensive radio receivers. In today's homodyne receivers, the only remaining filter is a band selection filter. If the band selection filter can be removed, much cost and space can be saved. This is especially true in multiband radio receiver front ends that require a band selection filter for each band. If a plurality of antennas are used, the effect is even higher.

  If a prefilter such as a band selection filter is simply removed, strong out-of-band interference will saturate the radio receiver. It will also cause intermodulation distortion and compression of the input signal. Different communication standards have different requirements for maximum out-of-band interference. For example, in order to fulfill the requirements according to the GSM (Global System for Mobile communication) standard, out-of-band interference up to 0 dBm must be handled. A conventional radio receiver front end cannot fulfill this requirement without a pre-filter such as a band selection filter.

  In some radio receiver front end designs, the band select filter may be integrated on the chip. However, this solution cannot fulfill the maximum out-of-band requirements of different mobile communication standards such as the GSM standard or the UMTS (Universal Mobile Telecommunication System) standard.

  Accordingly, it is an object of the present invention to provide a simpler wireless receiver front end than known in the art, which may be realized with on-chip technology. It is also an object of the present invention to provide a method for converting an input signal having a first frequency into an output signal having a second frequency.

  According to the first aspect of the invention, these objects are achieved with an N-phase radio receiver front end according to the invention, which does not have any on-chip or off-chip band selection filter.

  The N-phase radio receiver front end according to the present invention includes a low noise amplifier circuit, a mixer device and a signal generator. The input port of the N-phase radio receiver front end is directly connected to the input port of the low noise amplifier circuit. The mixer device is a current mode mixer device, and the input signal is not converted to a voltage before mixing. The output port of the low noise amplifier circuit is directly connected to the input port of the mixer device. A signal generator is employed to generate an N-phase phase shifted local oscillator signal. A phase shift local oscillator signal may be used to selectively activate the mixer core of the mixer device.

  The mixer device may include N / 2 mixer cores. Each mixer core may have an input terminal directly connected to the input port of the mixer device. The mixer core may be a single balanced or double balanced mixer core.

  The low noise amplifier circuit may be a single-ended or differential amplifier.

  The output port of the mixer device may be connected to an active or passive frequency selective load. The frequency selective load may comprise N / 2 current-voltage conversion means, whereby out-of-band interference of signal input on the radio receiver front end may be suppressed.

  Each current-voltage converting means may include a mixer load connected to each output terminal of the mixer core and the signal grounding means. Each mixer load may be a resistor connected in parallel with a capacitor. Each mixer load capacitor has an effective value for suppressing out-of-band interference of the input signal on the radio receiver front end when the input signal is mixed. The capacitance of each mixer load capacitor may be variable in order to suppress out-of-band interference of input signals having different bandwidths.

  The signal generator may be an oscillator that provides a signal that drives the mixer core. The oscillator may be a voltage controlled oscillator.

  The mixer device may be connected to a voltage controlled oscillator via a transformer to supply a local oscillator signal, such as an orthogonal local oscillator signal. Supplying a local oscillator signal via a transformer has the advantage that no low frequency noise is introduced into the local oscillator terminal of the mixer device.

  The local oscillator may include an orthogonal oscillator having an LC tank circuit. The inductor of the LC tank circuit may provide the primary winding of the transformer, and the inductor connected to the local oscillator input terminal of the mixer may provide the secondary winding of the transformer. In this way, no additional components are required to provide the transformer other than the inductor that provides the secondary winding.

  Each LC tank circuit capacitor may be a variable capacitor to adjust the frequency of the local oscillator signal.

  Alternatively, the signal generator may be provided by a high frequency oscillator and frequency divider arranged to provide N non-overlapping local oscillator signals having a duty cycle of approximately 1 / N. For quadrature oscillator signals, the duty cycle should be approximately 25% for each signal.

  According to a second aspect of the invention, the object is to provide an N-phase radio receiver according to the invention in a wireless electronic communication device for converting an input signal having a first frequency into a signal having a second frequency. Realized by using the front end.

  According to a third aspect of the present invention, the object is realized by a wireless electronic communication device comprising an N-phase wireless receiver front end according to the present invention.

  According to a fourth aspect of the present invention, the object is achieved by a method for converting an input signal having a first frequency into an output signal having a second frequency in an N-phase radio receiver front end. The The method includes receiving an input signal at an input port of a radio receiver front end, i.e., amplifying the input signal including out-of-band interference in a low-noise amplifier circuit. Mixing a plurality of phase shift local oscillator signals having a second frequency in the mixer device to generate a mixed signal having a second frequency.

  The mixed signal may include out-of-band interference. Further, the method may include a step of suppressing out-of-band interference of the mixed signal.

  The suppression step may comprise providing a mixed input signal including out-of-band interference to an active or passive frequency selective load. The frequency selective load may be a mixer load connected to each output terminal and signal grounding means of the mixer device. The mixed signal may be an IF signal.

  The suppression step may comprise suppression by a mixer load capacitor having a value effective to suppress out-of-band interference of the mixed signal.

  The method may be a variable capacitor with a frequency selective load that suppresses out-of-band interference of mixed input signals with different bandwidths, but may include adjusting the capacitance of the capacitor.

  The method may also include the steps of generating local oscillator signals and supplying the generated local oscillator signals to N / 2 mixer cores of the mixer device.

  Furthermore, the method may comprise adjusting the capacitance of an oscillator capacitor connected to the mixer device to adjust the frequency of the local oscillator signal.

  Further embodiments of the invention are defined in the dependent claims.

  An advantage of the present invention is that the size and complexity of the radio receiver front end is reduced compared to a conventional radio receiver front end.

  It should be emphasized that the term “comprising”, as used herein, specifies the presence of the described feature, integer, step or part, but one It does not exclude the presence or addition of other features, integers, steps, parts or groups thereof.

  FIG. 1 illustrates a mobile phone 1 as one exemplary wireless electronic communication device, in which an N-phase wireless receiver front end according to the present invention may be used. The present invention is not limited to the implementation in the mobile phone 1. The present invention is applied to a wide variety of electronic devices that require a radio receiver front end to receive and process radio frequency (RF) input signals, such as portable radio terminals, pagers, communicators, electronic organizers, or smart phones. You may implement. The mobile phone 1 may include a first antenna 10 and a second auxiliary antenna 11 in order to receive an input signal. The microphone 12, loudspeaker 13, keypad 14, and display 15 provide a man-machine interface for operating the mobile phone 1.

  In operation, the mobile phone is connected to a mobile communication network 21 such as GSM, UMTS, PCS (Personal Communication System) and / or PDC (Personal Digital Cellular) via the first radio link 22 by the first antenna 10. You may be connected to the radio station 20 (base station). Furthermore, the mobile phone 1 may establish a second wireless link to the peripheral device 30 via the second wireless link 31 by the second auxiliary antenna 11 during operation. The second wireless link 31 is, for example, a Bluetooth (registered trademark) link established in a 2.4 (2.400-2.480) GHz frequency band. In order to establish the radio links 22, 31, the mobile phone 1 may be equipped with radio resources that are adapted according to the relevant technology used. In this way, the mobile phone 1 is provided with a first wireless access means such as a transceiver for communicating wireless signals with the base station 20, and further with a second wireless device for communicating wireless signals with the peripheral device 30. Wireless access means. Alternatively, one wireless access means may be switchable to communicate a wireless signal with either the base station 20 or the peripheral device 30.

  Peripheral device 30 may be any device having wireless communication capability, such as via Bluetooth (Bluetooth) technology or any other wireless local area network (WLAN) technology. The device includes an antenna 32 for exchanging signals via the second link 31 and a transceiver (not shown) adapted according to the communication technology used by the peripheral device 30. The device may be a wireless headset, a remote server, a fax machine, a vending machine, a printer, a computer, or the like. A wide variety of electronic devices may have such communication capabilities and may need to transfer data wirelessly.

  Radio frequency (RF) received input signals may be processed by a radio receiver front end according to the present invention. The input signal may be single-ended or differential. The input signal is converted to an intermediate frequency (IF) signal and then further signal processing is performed. As described above, the wireless receiver front end of the mobile phone 1 includes a mixer device including one or several mixer cores for converting an input signal having the first frequency into an output signal having the second frequency. This may be provided and will be disclosed below.

  FIG. 2 shows a radio receiver front end according to the present invention. The antenna 10 may be directly connected to the input port of the low noise amplifier circuit (LNA) 50. For example, the LNA 50 is either linear or linearized so that it can handle out-of-band interference according to the GSM standard that should handle at least up to 0 dBm out-of-band interference. The RF signal input to the LNA 50 comprises both the desired signal and the superimposed out-of-band interference, which are amplified with the LNA 50 gain.

  The current input port of the N-phase mixer device 50a is connected to the output port of the LNA 50. The mixer apparatus 50a may include N / 2 mixer cores 51 and 52. In the embodiments of FIGS. 2, 3 and 6, an orthogonal radio receiver front end is described. These mixer devices 50a include first and second mixer cores 51 and 52 having input terminals. Each input port and output port of the mixer device 50a and the LNA 50 may include one or several terminals.

  The first mixer core 51 may be used for the I-channel of the input signal, and the second mixer core 52 may be used for the Q-channel of the input signal. The output port of the LNA 50 is directly connected to the input port of the mixer device, that is, the signal current from the LNA 50 is not converted into a voltage by the load impedance. With 0 dBm interference, the signal converted to voltage would be too large to handle. Therefore, in accordance with the present invention, the mixing is processed in the current domain, for example, by activating the mixer cores 51, 52 with a phase shifted LO signal to selectively activate the mixer device 50a. In this way, interference is handled.

Each mixer core 51, 52 and mixer device 50a also includes a local oscillator (LO) input terminal for receiving the LO signal generated by the LO signal generating means, that is, the LO signal generator, and the amplified input signal and Mixed. In order to receive the first phase first LO signal LO _I , the first mixer core 51 is employed and responds thereto. In order to receive and respond to the second LO signal LO _Q of the second phase different from the first phase, the second mixer core 52 is employed.

  The output port of the mixer device 50a, for example, the output terminals of the first and second mixer cores 51 and 52 may be connected to an active or passive frequency selective load.

The frequency selective load may include first and second current-voltage conversion means. In this way, the input signal now amplified and mixed with the lower frequency signal may be converted to voltage by the current-voltage conversion means. Thus, the I- and Q-channel output signals IF _I , IF _Q may be provided to the output port of the frequency selective load. Each output port of the frequency selective load may include first and second terminals.

  The frequency selective load will also function as a suppression means to suppress out-of-band interference.

  FIG. 3 is a circuit diagram of an embodiment of an N-phase radio receiver front end according to the present invention, where N = 4. Thus, the radio receiver front end according to FIG. 3 is an orthogonal radio receiver front end. With the design according to the present invention, it is important that the linearity of the LNA is sufficiently high and, as described above, for example, it is possible to handle out-of-band interference of up to 0 dBm. In the embodiment of FIG. 3, the LNA is a common gate or common base LNA, which may be an input transistor, but is provided by an amplification transistor 60. The transistor 60 may be an FET (Field Effect Transistor) such as a MOS (Metal Oxide Semiconductor) transistor or a BJT (Bipolar Junction Transistor). In the embodiment of FIG. 3, the LNA 50 is provided with a FET transistor. The input port of the orthogonal radio receiver front end is connected to the source terminal of the transistor 60.

The gate of the amplification transistor 60 is connected to the bias voltage V _bias1 . The bias input (gate) of the amplification transistor 60 is connected to a common mode feedback circuit in order to control the bias of the amplification transistor 60.

Since the mixer cores 51 and 52 and the first and second current-voltage conversion means 53 and 54 have the same design, only the mixer core 51 and the first current-voltage conversion means related thereto will be described in detail below. . The first mixer core 51 may include first and second mixer transistors 61 a and 62 a connected to the input terminal of the first mixer core 51. The mixer transistors 61a and 62a may be FET transistors or BJT transistors. The advantage of BJT transistors is that they are faster than FET transistors that provide relatively high linearity. In the embodiment of FIG. 3, the mixer transistors 61a, 62a are provided as BJT transistors. The emitters of the mixer transistors 61 a and 62 a are connected to the input terminal of the first mixer core 51. The base of each mixer transistor is connected to the LO (local oscillator) input terminal of the first mixer core 51. Each mixer transistor 61a, 62a is responsive to each of the quadrature LO signals. The first mixer transistor 61a is responsive to the first phase first quadrature LO signal LQ _{I +} . The second mixer transistor 62a is responsive to a second phase second quadrature LO signal LQ _I− that is 180 ° phase shifted with respect to the first phase. The collectors of the mixer transistors 61a and 62a are connected to the first and second output terminals of the first mixer core 51, respectively.

  The frequency selective load, for example, the current-voltage conversion means may include a capacitor 67a provided between the input terminals of the frequency selective load. Thus, the frequency selective load will operate as a filter for out-of-band interference and to provide some channel filter function.

  The mixer device 50a and the mixer cores 51 and 52 are current mode mixers that operate in a current region. The output signal of the first mixer core 51 is supplied to the frequency selective load. The frequency selective load may be provided with first current-voltage conversion means 53, and the output signal of the first mixer core 51 may be converted into voltage by the means. The first current-voltage conversion means 53 may include individual conversion means for each output signal. Each conversion means may include passive components such as capacitors 64a and 66b connected in parallel to the resistor 63a and the output terminal of the first mixer core 51, and signal grounding means such as a supply voltage. . The first mixer transistor 61a is connected to the resistor 63a and the capacitor 64a, and the second mixer transistor 62a is connected to the resistor 65a and the capacitor 66a.

  The first and second current-voltage conversion means may be provided with active components. For example, the resistor 63a and / or the resistor 65a may be replaced with a transistor connected to the resistor. Alternatively, the first and second current-voltage conversion means 53 and 54 may be provided with transistor amplifiers in order to convert the current signal output from the mixer device 50a. The transfer function of such a transimpedance amplifier can be given frequency selectivity.

An I-channel first IF (intermediate frequency) output signal IF _I may be generated between the output terminals of the first mixer core 51. The desired signal centered at low frequency is not significantly attenuated by capacitors 64a, 66a and 67a. However, in GSM, out-of-band interference that would occur at frequencies that are at least 20 MHz offset from its desired signal would be greatly attenuated if the values of capacitors 64a, 66a and 67a are properly selected. . Furthermore, it is possible to use a single balanced mixer core and a single-ended LNA, and capacitors 64a, 66a and 67a suppress leakage from the LO to the IF. Single-ended LNA eliminates the need for an external balun. The external filter may perform a balun function. Therefore, if a differential LNA is used, it may be necessary to attach a single external balun. The signal after the radio receiver front end is differential, which is suitable for subsequent on-chip processing.

  Instead of the LNA 50, a feedback LNA having sufficient linearity to handle up to 0 dBm out-of-band interference may be used to meet the GSM standard. However, this linearity requirement must be considered in each particular case.

The second mixer core 52 may include first and second mixer transistors 61 b and 62 b and is configured in the same manner as the first mixer core 51. The second current-voltage conversion means 54 includes a mixer load provided by resistors 63 b and 65 b and capacitors 64 b and 66 b and a capacitor 67 b disposed between the input terminals of the second current-voltage conversion means 54. The first mixer transistor 61b of the second mixer core 52 is responsive to a third phase, ie, a third quadrature LO signal LO _{Q +} that is 90 ° phase shifted relative to the first phase. The second mixer transistor 62b of the second mixer core 53 is responsive to a fourth phase, ie, a fourth quadrature LO signal LO _Q− that is phase shifted 270 ° relative to the first phase. The collectors of the mixer transistors 61 b and 62 b of the second mixer core 52 are connected to the first and second output terminals of the second mixer core 52.

The Q-channel second IF (intermediate frequency) output signal IF _Q may be output between the output terminals of the second mixer core 52.

  A current device 68 is connected to the input port of the radio receiver front end and the input port of the LNA 50 to provide a bias current for the radio receiver front end. The current device 68 may be provided, for example, as a resistor, an inductor, or a transistor connected as a current source. The advantage of an inductor is that the voltage drop there is lower than a transistor connected as a resistor or current source. Further, when the current device 68 is provided by an inductor, the parasitic capacitance generated at the source of the transistor 60 can be ignored by the inductor.

The LO input terminals of the first and second mixer cores 51 and 52 are connected to the LO signal generator. In one embodiment, the LO signal generator is a quadrature LO signal generator. Since the signal to out-of-band interference ratio is not improved if the input signal is filtered before it is applied to the mixer device 50a, the phase noise of the LO signal can be a large offset, for example greater than 20 MHz, in a GSM implementation. In frequency, it must be very low. If the phase noise is too high, it is possible to prevent the reception of weak signals due to the mutual mixing of strong out-of-band interference. In the case of GSM, the phase noise requirement will be similar to that required at the transmitter. Thus, the same or similar oscillators may be used to generate the LO signals LO _{I +} , LO _I− , LO _{Q +} , LO _Q− for the transmitter and radio receiver front end. Also, since it is transferred directly to the IF output, the low frequency local oscillator noise must also be low.

  The signal generator may include an oscillator such as a VCO (voltage controlled oscillator).

  FIG. 4a shows one embodiment of a VCO (Voltage Controlled Oscillator) used to generate a quadrature LO signal. Generation of a low phase noise local oscillator signal essentially free of low frequency noise is possible by using an oscillator with an LC tank. The LC tank may be part of a transformer having a secondary winding connected to the mixer cores 51 and 52. In this case, no local oscillator buffer is required and the DC level of the local oscillator signal supplied to the mixer core will be easily set. The VCO includes four sets of transistors 71a, 71b, 72a, 72b, 73a, 73b, 74a, and 74b. The transistor may be an FET or BJT transistor.

The source of the transistor 71a is connected to the drain of the transistor 71b. The gate of the transistor 71a is connected to the drain of the transistor 73a, and the drain of the transistor 71a is connected to a first LC tank including an inductor connected in parallel with the capacitor 76. The center tap of the inductor 75 is connected to the supply voltage. The value of the capacitor 76 sets the VCO frequency. The gate of transistor 71b is connected to the drain of transistor 72a and the gate of transistor 73a. The source of the transistor 71 b is connected to the drain of the bias transistor 79. The gate of the bias transistor 79 will receive the bias voltage V _bias3 during operation. The source of the bias transistor 79 is connected to the grounding means.

  The drain of transistor 72a is connected to the second terminals of inductor 75 and capacitor 76 and the gates of transistors 73a and 71b. The gate of transistor 72a is connected to the drain of transistor 74a. The source of transistor 72a is connected to the drain of transistor 72b. The gate of transistor 72b is connected to the drain of transistor 71a and the gate of transistor 74a. The source of the transistor 72 b is connected to the drain of the bias transistor 79.

The source of the transistor 73a is connected to the drain of the transistor 73b. The gate of transistor 73a is connected to the drain of transistor 72a, and the drain of transistor 73a is connected to the second LC tank including inductor 77 connected in parallel with capacitor 78 and the gate of transistor 71a. The center tap of inductor 77 is connected to the supply voltage. The value of capacitor 78 should track the value of capacitor 76, which sets the frequency of the VCO. The gate of transistor 73b is connected to the drain of transistor 74a and the gate of transistor 72a. The source of the transistor 73b is connected to the drain of the bias transistor 80. The gate of the bias transistor 80 will receive a bias voltage V _bias3 during operation. The source of the bias transistor 80 is connected to the grounding means.

  The drain of the transistor 74a is connected to the second terminals of the inductor 77 and the capacitor 78 and the gates of the transistors 72a and 73b. The gate of transistor 74a is connected to the drain of transistor 71a. The source of the transistor 74a is connected to the drain of the transistor 74b. The gate of transistor 74b is connected to the gate of transistor 71a and the drain of transistor 73a. The source of the transistor 74 b is connected to the drain of the bias transistor 80.

  The VCO is magnetically coupled to the LO input terminals of the mixer cores 51 and 52 by first and second transformers. The first transformer may include an inductor 75 and an inductor 81 connected to the gate of the transistor 61a and the gate of the transistor 62a. The primary winding of the first transformer is provided by an inductor 75, and its secondary winding is provided by an inductor 81. Similarly, the second transformer may include an inductor 77 and an inductor 82 connected to the gate of the transistor 61b and the gate of the transistor 62b.

Supplying the LO signals LO _{I +} , LO _I− , LO _{Q +} , LO _Q− to the mixer transistors 61a, 61b, 62a, 62b through the transformer does not apply any low frequency noise to the LO input terminals of the mixer cores 51, 52. It means deafness. Inductors 81 and 82 will short out all low frequency noise at the LO input terminal. Furthermore, the transformer does not consume any current since it contains only passive components, so it is an advantage if low power consumption is important.

  FIG. 4b shows the LO signal being generated by the VCO according to the embodiment of FIG. 4a. At each instant, the LO signal at the highest voltage level will dominate the other LO signals due to the phase shift of the signal, except at the intersection of the LO signals. This means that the input terminals of the mixer cores 51 and 52 can be connected to each other. The transistor that receives the LO signal at the highest voltage level will become conductive and will therefore operate. In addition, the transistor that receives the LO signal at the highest voltage level will dominate the other transistors in the mixer device 50a, even though all other transistors are somewhat conductive.

FIG. 5a shows another solution for generating LO signals LO _{I +} , LO _I− , LO _{Q +} , LO _Q− with sufficiently low phase noise and low frequency noise and phase shifted relative to each other. . In this embodiment, the LO signal is phase shifted so that substantially only one signal will be in the high state at that time. The high frequency oscillator 90 is connected to the digital frequency divider 91. In this embodiment, the frequency divider is arranged to generate quadrature LO signals, eg, four LO signals LO _{I +} , LO _I− , LO _{Q +} , LO _Q− where only one signal is active at a time _. Has been. The frequency of the high frequency oscillator should be at least twice the frequency of the output signal from the digital frequency divider 91. It is important to avoid overlap during times when one or more of the four local oscillator signals are high at the same time. For approximately 1 / N, eg, quadrature signals, the overlap can be avoided by placing the frequency divider 91 to provide a 25% duty cycle for each output signal. If there is an overlap, extra noise is generated and the sensitivity to mixer transistor matching inaccuracies increases. However, some overlap may be allowed if the noise requirements are less stringent. The advantage of the high frequency oscillator 90 and the digital frequency divider 91 is that the current consumption is increased compared to the VCO embodiment of FIG. 4a, but a smaller design is possible.

  The frequency divider 91 may be provided by a Johnson counter in which N flip-flops are connected in series and the output signal of the final stage flip-flop is supplied to the first flip-flop back to the input terminal. All flip-flops should be clocked with the same clock signal as N times the frequency of the output signal. In order to avoid loops in the wrong state, only one output must be forced high at a time. As a result, N LO signals are taken out to the outputs of N flip-flops.

  FIG. 5 b shows the phase-shifted LO signal generated by frequency divider 91 when N = 4. The LO signal is basically a non-overlapping square wave.

In the above description, the input signal RF _in is a single-ended type. However, the input signal may be differential as well, where the LNA 50 is arranged to amplify the differential signal and then the signal is single balanced mixer core as described above. Instead of being supplied to the double balanced mixer core.

  As explained above, the radio receiver front-end may be adapted for dual-mode mobile communications, where it handles input signals from at least two mobile communications networks applying different communication standards such as GSM and UMTS. May be. Two radio receiver front ends as described above may be arranged in parallel to provide a dual mode radio receiver front end, where each front end is adapted according to an individual standard. The parallel connection circuit may be selectively activated by selectively biasing the LNA of each radio receiver front-end circuit. A control device may be arranged to control the LNA bias of each circuit.

  Alternatively, a dual mode radio receiver front end may be provided, for example, by changing the bandwidth of the frequency selective load of the current-voltage conversion means 53, 54. Therefore, if the capacitors 64a, 64b and 67a are variable capacitors having a capacitance value that can be selectively varied, a control device is arranged so that the capacitors 64a, 64b and 67a are set to specific values. Also good. The set value will be selected such that out-of-band interference of input signals with different received signal bandwidths is suppressed and the signal to be received is essentially unaffected.

  According to the present invention, one topology is chosen so that the LNA 50 and the mixer device 50a have sufficient linearity to handle out-of-band interference. If the LNA and mixer device are not sufficiently linear, out-of-band interference will cause intermodulation distortion and compression of the input signal, as the band select filter is eliminated by the present invention.

  FIG. 6 is a circuit diagram showing another embodiment of an N-phase radio receiver front end according to the present invention. In the illustrated embodiment, N = 4, ie, a quadrature radio receiver front end. Embodiment Parts corresponding to those in FIG. 3 are denoted by the same reference numerals, and description related to FIG. 6 is omitted. However, it should be noted that even if the part is equivalent, its value may vary depending on the actual implementation.

The radio receiver front end shown in FIG. 6 includes a double balanced mixer device having a differential LNA. The differential amplifier comprises first and second amplifier means provided by first and second amplifier transistors 160a, 160b, for example MOS or BJT transistors. The input port of the orthogonal radio receiver front end is connected to the input port of the LNA 50, and the input port is directly connected to the source terminals of the transistors 160a and 160b to which the input signal RF _in is applied.

The gates of transistors 160a and 160b are connected to bias voltage _Vbias . Alternatively, the bias inputs (gates) of the transistors 160a and 160b may be connected to a common mode feedback circuit (not shown) that controls the bias of the transistors 160a and 160b.

The first and second mixer cores 51 and 52 according to the embodiment of FIG. 6 include four mixer transistors 161a, 161b, 161c, 161d, 162a, 162b, 162c, and 162d, respectively. The gates of transistors 161a and 162c are connected to receive the local oscillator signal LO _{Q +} . The gates of transistors 161b and 162d are connected to receive the local oscillator signal LO _{I +} . The gates of transistors 161c and 162a are connected to receive the local oscillator signal LO _Q- . The gates of transistors 161d and 162b are connected and receive the local oscillator signal LO _I- .

  The drains of the transistors 161a and 162b are connected to the capacitor 64a, the resistor 63a, and the first terminal of the capacitor 67a. The drains of the transistors 161b and 162a are connected to the first terminals of the capacitor 64b, the resistor 63b, and the capacitor 67b. The drains of the transistors 161c and 162d are connected to the first terminal of the capacitor 66b and the resistor 65b and the second terminal of the capacitor 67b. The drains of the transistors 161d and 162c are connected to the first terminal of the capacitor 66a and the resistor 65a and to the second terminal of the capacitor 67a.

During operation, the first output signal IF _I is generated between the output terminals connected to the terminal of the capacitor 67a, and the second output signal IF _Q is generated between the output terminals connected to the terminal of the capacitor 67b. The

The local oscillator signals LO _{I +} , LO _I− , LO _{Q +} , LO _Q− may be provided according to the principles described in connection with FIGS. 4a-4b or FIGS. 5a-5b.

  FIG. 7 shows a method according to the invention. In the first step 100, an input signal including out-of-band interference is received at the input port of the N-phase radio receiver front end. In step 101, an input signal including out-of-band interference is amplified by the LNA 50. Thereafter, in step 102, the amplified input signal and out-of-band interference are mixed with the phase-shifted LO signal as described above to produce a mixed signal that includes out-of-band interference. Finally, in step 103, as described above, for example, the mixed signal is supplied to a frequency selective load, eg, a mixer load comprising a resistor and a capacitor, thereby suppressing out-of-band interference of the mixed signal. If the frequency selective load includes a mixer load, the mixer load capacitors 64a, 66a, 64b, 66b, 67a, 67b may be effective values for suppressing out-of-band interference. If the capacitor is a variable capacitor, the method may include the step of setting the capacitor value. In addition, the method may include a step of supplying an LO signal to the mixer cores 51 and 52. Further, if the capacitors 76, 78 of the VCO LC tank are variable, the method may include the step of setting the capacitor value.

  In the past, the N-phase radio receiver front end has been concerned. The N-phase radio receiver may be a quadrature radio receiver front end. However, in practice, any number of phases may be processed if the front end is appropriately arranged. For example, in the case of 6 phases, processing may be performed by adding one additional mixer core to the mixer apparatus 50a according to the embodiment of FIG. 4a. Therefore, the number of different LO signals to be generated will be 6. The appropriate number of LO signals may be generated by designing a VCO by a frequency divider or by the principle of the embodiment of FIG. 4a. The number of phases to be processed may be displayed as N. Therefore, the number of different LO signals to be generated will be N. In this way, the LO signals will shift with a phase of 360 ° / N relative to each other.

  The present invention may be used, for example, to downconvert an RF signal to a zero IF or low IF signal without using any band select filter. Therefore, the front end according to the present invention can be compactly designed and inexpensive to manufacture.

  An advantage of embodiments of the present invention is that no band selection filter is required at the orthogonal radio receiver front end to suppress out-of-band interference. Therefore, if the front end is implemented using on-chip technology, the production cost is lower compared to a conventional radio receiver front end with a band select filter provided either on or off-chip. It may be.

  The present invention has been described above with reference to specific embodiments. However, other embodiments than the above described are equally possible within the scope of the invention. Various features of the present invention may be integrated in other combinations other than those described above. The invention is only limited by the appended claims.

Further objects, features and advantages of the present invention will become apparent from the following detailed description of the invention and the relationship to the accompanying drawings below.
It is a figure which shows the front of the mobile communication apparatus containing the N-phase radio receiver front end by this invention. FIG. 3 is a block diagram illustrating an N-phase radio receiver front end according to the present invention. FIG. 2 is a circuit diagram showing an embodiment of an N-phase radio receiver front end according to the present invention. FIG. 2 is a circuit diagram illustrating a first embodiment of a voltage controlled oscillator for generating a low noise local oscillator signal. It is a signal waveform diagram which shows a local oscillator signal. FIG. 3 is a block diagram illustrating a high frequency oscillator connected to a frequency divider for generating a low noise local oscillator signal. It is a signal waveform diagram which shows a local oscillator signal. It is a circuit diagram which shows other embodiment of the N-phase radio | wireless receiver front end by this invention. 4 is a flowchart illustrating one embodiment of a method according to the present invention.

Claims (36)

A low noise amplifier circuit (50, 60) having an input port, an input port and an output port, a mixer device (50a) having an input port and an output port, and applied to generate N local oscillator signals; An N-phase radio receiver front end for converting an input signal having a first frequency into an output signal having a second frequency, comprising a signal generator connected to the mixer device to operate. ,
The input port of the front end of the N-phase radio receiver is directly connected to the input port of the low noise amplifier circuit (50, 60),
The mixer device is a current mode type mixer device,
The output port of the low noise amplifier circuit is directly connected to the input port of the mixer device,
N-phase radio receiver front end, wherein the signal generator is applied to generate an N-phase phase-shifted local oscillator signal.   The mixer apparatus (50a) comprises N / 2 mixer cores (51, 52), each mixer core comprising an input terminal connected directly to the input port of the mixer apparatus. Phase radio receiver front end.   The N-phase radio receiver front end according to claim 2, wherein the mixer core (51, 52) is a single balanced or double balanced mixer core.   The N-phase radio receiver front end according to any one of claims 1 to 3, wherein the low-noise amplifier circuit is a differential amplifier (160a, 160b) or a single-ended amplifier (60).   Each mixer core (51, 52) includes two or four transistors (61a, 62a, 61b, 62b, 161a, 161b, 161c, 161d, 162a, 162b, 162c, 162d), and the transistors of each mixer core are 2 4. An N-phase radio receiver front end according to claim 2 or 3 responsive to two different local oscillator signals.   The N-phase radio receiver front end according to any one of claims 1 to 5, wherein the signal generator is an oscillator that provides the local oscillator signal that drives the mixer device (50a).   The signal generator operates on the mixer device (50a) via a transformer (75, 77, 81, 82) to provide the local oscillator signal to a local oscillator input terminal of the mixer device (50a). The N-phase radio receiver front end according to any one of claims 1 to 6, which is an oscillator connected in this manner.   The N-phase radio receiver front end of claim 7, wherein the oscillator is a quadrature oscillator that provides a quadrature local oscillator signal.   The N-phase radio receiver front end according to claim 7 or 8, wherein the oscillator comprises an LC tank, each LC tank being provided by an inductor (75, 77) and a capacitor (76, 78). The inductors (75, 77) of the LC tank provide the primary winding of the transformer;
10. The N-phase radio receiver front end according to claim 9, wherein an inductor (81, 82) connected to the local oscillator input terminal of the mixer device (50a) provides a secondary winding of the transformer.   11. An N-phase radio receiver front end according to claim 9 or 10, wherein the capacitors (76, 78) of each LC tank are variable capacitors for adjusting the frequency of the local oscillator signal.   The N-phase radio receiver front end according to any one of claims 1 to 6, wherein the signal generator comprises a high frequency oscillator (90) and a frequency divider (91) for providing the local oscillator signal.   13. The frequency divider (91) is configured to provide N local oscillator signals having a duty cycle of 1 / N and only one of the local oscillator signals is in a high state at a time. The described N-phase radio receiver front end.   14. The N-phase radio receiver front end according to any one of the preceding claims, wherein the low noise amplifier circuit (50) comprises at least one input transistor (60) connected in a common gate or common base configuration. .   15. The N-phase radio receiver front end according to any one of the preceding claims, further comprising an active or passive frequency selective load connected to the output port of the mixer device (50a).   The N-phase radio receiver according to claim 15, wherein the frequency selective load comprises current-voltage conversion means (53, 54, 63a, 64a, 65a, 66a, 63b, 64b, 65b, 66b, 67a, 67b). front end. The output port of the first mixer core (51) of the mixer device (50a) is connected to the first current-voltage conversion means,
17. The N-phase radio receiver front end according to claim 16, wherein an output port of the second mixer core (52) of the mixer device is connected to second current-voltage conversion means.   Each current-voltage conversion means (53, 54, 63a, 64a, 65a, 66a, 63b, 64b, 65b, 66b, 67a, 67b) is a mixer load connected to each output port of the mixer core and signal grounding means. The N-phase radio receiver front end according to claim 17, comprising: Each mixer load is a resistor (63a, 65a, 63b, 65b) connected in parallel with a capacitor (64a, 66a, 64b, 66b),
The N-phase radio receiver front end according to claim 18, wherein a capacitor (67a, 67b) is connected between the output terminals of each mixer core.   The capacitors (64a, 66a, 64b, 66b, 67a, 67b) of each mixer load are effective in suppressing out-of-band interference of signals input to the radio receiver front end when the signals are mixed. 20. The N-phase radio receiver front end of claim 19 having a typical value.   21. The capacitance of each capacitor (64a, 66a, 64b, 66b, 67a, 67b) of each mixer load is variable to suppress out-of-band interference of mixed input signals having different bandwidths. N-phase radio receiver front end as described in.   The N-phase radio receiver front end according to any one of claims 1 to 21, further comprising a current device (68) connected to the input port of the low noise amplifier circuit and a grounding means.   23. The N-phase radio receiver front end according to claim 22, wherein the current device (68) is an inductor, a resistor, or a transistor connected as a current source.   The N-phase radio receiver front end according to any one of claims 1 to 23, wherein the N-phase radio receiver front end is an orthogonal radio receiver front end.   25. An N-phase radio receiver front end according to any one of claims 1 to 24 in a wireless electronic communication device (1) for converting an input signal having a first frequency into an output signal having a second frequency. use.   A wireless electronic communication device (1) comprising the N-phase wireless receiver front end according to any one of claims 1 to 24.   24. The wireless electronic communication device according to claim 23, wherein the wireless electronic communication device (1) is a portable wireless terminal, a pager, a communicator, an electronic organizer, or a smartphone.   24. The wireless electronic communication device according to claim 23, wherein the wireless electronic communication device (1) is a mobile phone. A method for converting an input signal having a first frequency into an output signal having a second frequency in an N-phase radio receiver front end, comprising:
The method comprises receiving the input signal at an input port of the wireless receiver front end;
Amplifying the input signal including out-of-band interference with a low noise amplifier circuit (50, 60);
A plurality of phase-shifted local oscillator signals having a second frequency and the input signal and the out-of-band interference in a current mode mixer device (50a) to generate a mixed signal having the second frequency. And mixing with the method. The mixed signal includes out-of-band interference;
30. The method of claim 29, further comprising suppressing the out-of-band interference of the mixed signal using a frequency selective load.   In the suppressing step, the mixed signal including the out-of-band interference is subjected to frequency selective loads (53, 54, 63a, 64a, 65a, respectively) connected to an output port of the mixer device (50a) and a signal grounding means. The method according to claim 30, comprising the step of feeding to 66a, 63b, 64b, 65b, 66b, 67a, 67b).   In the suppressing step, the mixed signal including the out-of-band interference is connected to a resistor (63a, 65a, 63b, 65b) in parallel with a capacitor (64a, 66a, 64b, 66b), and an output of the mixer device 32. The method according to claim 31, comprising the step of feeding to a capacitor (67a, 67b) connected between the terminals.   33. The step of claim 32, wherein the step of suppressing comprises suppressing by a capacitor (64a, 66a, 64b, 66b, 67a, 67b) having a value effective to suppress out-of-band interference of the mixed signal. Method.   Adjusting the capacitance of capacitors (64a, 66a, 64b, 66b, 67a, 67b) that are variable capacitors with frequency selective loads that suppress out-of-band interference of mixed input signals having different bandwidths. 34. The method of claim 33, further comprising: Generating the local oscillator signal;
Supplying the generated local oscillator signal to the first and second single balanced or double balanced mixer cores (51, 52) of the mixer device (50a). The method according to claim 1.   36. The method of claim 35, further comprising adjusting a capacitance of an oscillator capacitor (76, 78) connected to the mixer device (50a) to adjust the frequency of the local oscillator signal.

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