KR20030033850A - Circuit for receiving radio frequency signal in dual band receiver - Google Patents

Abstract

PURPOSE: A circuit for receiving RF(Radio Frequency) signals of a dual band receiver is provided to enable the receiving of dual band signals while using only one VCO(Voltage Controlled Oscillator), so as to simply configure the dual band receiver. CONSTITUTION: A VCO(100) includes an impedance matching circuit in an output end thereof for setting the output power levels of reference frequency signals oscillated as local oscillating frequency signals corresponding to the first frequency band and the second harmonic signal components thereof to be similar each other. The first BPF(Band Pass Filter)(102) passes only the reference frequency signals. The second BPF(104) passes only the second harmonic signals. The first mixer(106) mixes RF signals of the first frequency band and the reference frequency signals passing the first BPF(102), to generate IF(Intermediate Frequency) signals. The second mixer(108) mixes RF signals of the second frequency band with the second harmonic component signals passing the second BPF(104), to generate signals that are fixed number times the as much as IF signals. And a frequency division circuit(110) divides output signals of the second mixer(108) to generate the IF signals.

Description

High frequency signal receiving circuit of dual band receiver {CIRCUIT FOR RECEIVING RADIO FREQUENCY SIGNAL IN DUAL BAND RECEIVER}

The present invention relates to a dual band receiver for receiving radio frequency (RF) signals of two different frequency bands, and more particularly to an RF signal receiving circuit for converting a received RF signal into an intermediate frequency signal. will be.

In the RF signal receiving circuit of a system that receives RF signals of two different frequency bands such as a dual band mobile communication terminal, each frequency is converted into an intermediate frequency (IF) signal in order to convert the RF signal of the received frequency band into an IF signal. A local oscillation frequency signal corresponding to the band is required.

Recently, the development of a cellular mobile communication terminal or a PCS mobile communication terminal capable of receiving a GPS (Global Positioning System) signal has been promoted. The receiver of such a mobile communication terminal should be designed as a dual band receiver to receive RF signals of two frequency bands, that is, a cellular frequency band and a GPS frequency band, or a PCS frequency band and a GPS frequency band. To this end, the RF signal receiving circuit of the mobile communication terminal requires a local oscillation frequency signal corresponding to a cellular frequency band or a PCS frequency band and a local oscillation frequency signal corresponding to a GPS frequency band.

For example, in the case of a model receiving a CDMA (J-CDMA: Japan-Code Division Mutiple Access) signal and a GPS signal currently being developed, a voltage controlled oscillator (VCO: PLL (Phase Locked Loop) using Voltage Controlled Oscillator is used as local oscillator. The signal of 2 GHz band generated from the local oscillator is divided into 2 GHz by the RFR3300, which is a Qualcomm RF receiver circuit, and is converted into a signal of 1 GHz band and used as a local oscillation frequency signal for CDMA transmission and reception signals. As a local oscillation frequency signal for receiving a GPS signal, a signal of 2 GHz band is directly used.

As described in the above example, in order to satisfy both the CDMA frequency band and the GPS frequency band by using the VCO of the 2 GHz band, a PLL including a VCO satisfying a wide frequency band is required. In addition, Qualcomm's RFR3300 solution, designed to receive GPS signals, is for J-CDMA and cannot be applied in countries with different frequencies than Japan.

Thus, for example, in order to make a mobile communication terminal capable of receiving both CDMA 2000 and GPS signals in Korea, a local oscillation frequency signal for GPS signal processing other than a conventional PLL that generates a local oscillation frequency signal for CDMA 2000 signal processing You must add a PLL that generates.

On the other hand, International Publication No. WO 1999/19981 filed under international application number PCT / US1998 / 21324 entitled "Dual band voltage controlled oscillator" and published on April 22, 1999 (Domestic Publication No .: 2001-0024518) Discloses a VCO operating in two distant frequency bands, for example 900 MHz and 1.8 GHz. According to this, a dual band device has a fully isolated local oscillator having a combiner network, a local oscillator having a double or triple multiple frequency multiplier, a pin diode or other similar RF switching device and an operating frequency range in which the two bands overlap. It includes an extremely wide band oscillator. Among them, the use of a fully isolated local oscillator with a combiner network has the drawback of requiring two complete sets of VCO circuits in addition to the combiner network circuit, and using a local oscillator with a frequency multiplier is always a spurious signal at the output. ), The pin diode requires a sufficient DC current to achieve a low "on" impedance, and the pin diode can produce high levels of harmonics associated with unwanted signals when the pin diode is "off". Extreme wideband oscillators inevitably have the drawback of being very sensitive to tuning control. Accordingly, the above-mentioned International Publication No. WO 1999/19981 includes two negative resistance generators sharing a common tunable tank circuit and a common impedance matching coupler circuit providing an RF output, depending on the frequency band currently being used. Disclosed is a VCO that selectively couples two negative resistance generators to a tank circuit to selectively oscillate signals of different frequency bands.

However, if the VCO according to International Publication No. WO 1999/19981 is applied to an RF signal receiving circuit of a dual band receiver that receives RF signals of a cellular frequency band and a GPS frequency band, or a PCS frequency band and a GPS frequency band, The configuration is still complicated because the device must have two negative resistance generators and can be configured to couple them selectively to the tank circuit.

Accordingly, an object of the present invention is to provide an RF signal receiving circuit which can simplify the configuration of a dual band receiver by allowing a dual band signal to be received while using only one VCO having a conventional circuit configuration.

1 is a block diagram of a high frequency signal receiving circuit according to an embodiment of the present invention;

2 is a detailed circuit diagram of a conventional voltage controlled oscillator (VCO) having an impedance matching circuit;

3 is a view showing a harmonic characteristics simulation result of a voltage controlled oscillator (VCO) according to an embodiment of the present invention.

In order to achieve the above object, the present invention provides an IF signal for the first and second frequency bands in a dual band receiver for receiving an RF signal of a first frequency band and an RF signal of a second frequency band higher than the first frequency band. In an RF signal receiving circuit for converting into a signal, an impedance matching set so that a reference frequency signal oscillating as a local oscillation frequency signal corresponding to a first frequency band and an output power level of its second harmonic signal component are similar to each other. A VCO having a circuit at its output, a first band pass filter (BPF) connected to the output of the VCO to pass only a reference frequency signal, and a second to pass only the second harmonic signal connected to the output of the VCO. A first mixer for generating an IF signal by mixing the BPF, the RF signal of the first frequency band and the reference frequency signal that has passed through the first BPF, and the RF signal of the second frequency band; And a second mixer for mixing a second harmonic component signal passing through 2 BPF to generate a signal that is an integer multiple of IF, and a divider circuit for dividing an output signal of the second mixer to generate an IF signal. .

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description and the annexed drawings, detailed descriptions of well-known functions and configurations that may unnecessarily obscure the subject matter of the present invention will be omitted.

1 is a block diagram of an RF signal receiving circuit according to an embodiment of the present invention. As described above, a mobile communication for receiving an RF signal of a cellular frequency band and a GPS frequency band, or a PCS frequency band and a GPS frequency band is described. A block diagram of an RF signal receiving circuit for use in a dual band receiver of a terminal is shown. In FIG. 1, the VCO 100 uses an impedance matching circuit provided at an output terminal to set the output power level of the reference frequency signal and its first harmonic signal component, that is, the second harmonic signal component, to be similar. The VCO 100 is included in a PLL (not shown) for generating a local oscillation frequency as in a typical mobile communication terminal, and the rest of the PLL is not directly related to the description of the present invention. Omitted without.

In general, in the mobile communication terminal, the frequency band is selected by the VCO in the PLL. The VCO is an active component, which inevitably has a harmonic component that is an integer multiple of the oscillation frequency. Typically, when designing a VCO, an appropriate impedance matching circuit is constructed at the VCO's RF output to eliminate these harmonics, leaving only the desired oscillation frequency and eliminating the remaining harmonics.

2 is a detailed circuit diagram showing an example of a conventional VCO having an impedance matching circuit. In FIG. 2, the resistors R1 to R4 are bias resistors that determine operating points of the transistors Q1 to Q2. Accordingly, the voltage applied as the bias power supply Vcc is distributed to the proper voltage by the resistors R1 to R3 to operate the transistors Q1 to Q2. In addition, the transistor Q1 operates as a collector ground, so that the emitter terminal of the transistor Q1 has a resistance (the emitter terminal of the transistor Q1) from the voltage distributed by the resistors R1 to R3. The same emitter current flows as the current generated by R4). Capacitor C4 is for determining the ground state of transistors Q1 to Q2, and by this capacitor C4 transistor Q2 is at the emitter ground (common emitter) state and transistor Q1. Will act as collector ground. The capacitor C1 couples the negative resistance formed by the negative resistance circuit 204 to the resonant circuit 200, and the DC voltage applied by the oscillation control voltage Vt provided to the power supply Vcc and the resonant circuit 200. It acts as a capacitor for direct current block to block flow. The oscillation control voltage Vt is applied from a loop filter (not shown) of the PLL including the VCO of FIG. The capacitor C2 is a capacitor for transferring the oscillation voltage obtained through the negative resistance of the transistor Q2 to the transistor Q2 in the emitter ground state. Accordingly, the transistor Q1 operates as an oscillation circuit, and the transistor Q2 operates in an emitter ground state to amplify a voltage applied to the base terminal. The amplified signal is removed by the impedance matching circuit 202 composed of the transistor Q2 and the capacitors Cm1 to Cm2 so that unnecessary harmonic components are removed and the required oscillation frequency signal is delivered to the load of 50 kHz at maximum power. do. As described above, the voltage appropriately distributed by the resistors R1 to R4 causes the oscillation to occur at a desired frequency by the negative resistance value formed by the transistor Q1 and the resonance circuit 200, and thus the oscillated frequency signal The signal is amplified by being applied to the transistor Q2 operating with the emitter ground and then output by the impedance matching circuit 202.

The present invention, unlike the elimination of all unnecessary harmonic components except the reference frequency signal in the impedance matching circuit 202 provided at the RF output terminal of the conventional VCO as described above, the output power level of the reference frequency signal and the second harmonic component The circuit constant is set to be similar and used as the VCO 100 of FIG. The circuit constant denotes a capacitance value of the capacitors Cm1 to Cm2. In this way, the reference frequency signal oscillated by the VCO 100 is operated at the local oscillation frequency of the cellular frequency band or the PCS frequency band, and the second harmonic signal output similar to the output power level of the reference frequency signal is a GPS signal. Use as local oscillation frequency signal to receive.

On the other hand, as an example of a technique using the second harmonic component in the VCO, a voltage controlled oscillator having a dual output is registered in Korean Patent Application No. 10-1997-0022745 and registered on May 2, 2000. Phase locked loop circuit. However, according to the above registration number 10-0262482, unlike the present invention, when the oscillation frequency is low, it is mentioned to use the second harmonic whose level is lower than the reference frequency.

When the two frequency bands received by the dual band receiver to which the RF receiver circuit of FIG. 1 is applied are called first and second frequency bands, in FIG. 1, reference numerals RF1 and RF2 denote first and second frequency bands, respectively. And RF and 2fo represent the reference frequency and the second harmonic of the VCO 100, respectively. Assuming that the first frequency band is the frequency band of CDMA2000 and the second frequency band is the GPS signal frequency, the frequency band of RF1 is 824.38 MHz to 849.38 MHz and the frequency of RF2 is 1575.42 MHz. In the CDMA2000 mobile communication terminal, the local oscillation frequency reference frequency band is 954.38 MHz to 979.38 MHz, and the second harmonic component of the reference frequency signal has a frequency band of 1908.76 MHz to 1958.76 MHz, which is twice the reference frequency band.

The VCO 100 simulates the values of the capacitors Cm1 to Cm2 of the impedance matching circuit 202 in the VCO as shown in FIG. 2 which oscillates the reference frequency of the frequency band used in the conventional CDMA2000. By setting the output power level of the second harmonic component to be similar to the output power level of the reference frequency component of the CDMA2000 as shown in FIG. Figure 3 shows the simulation results using Hewlett-Packard (HP) of the high frequency circuit design simulator MDS (Microwave Design System). Accordingly, the oscillation output signal from the VCO 100 is a reference frequency signal component fo for use as a local oscillation frequency of a conventional CDMA2000 transmit / receive RF signal and a second harmonic for use as a local oscillation frequency for GPS signal reception. It has component 2fo.

If the dual band receiver employing the RF signal receiving circuit of Fig. 1 operates in the CDMA2000 mode, the VCO 100 is phase locked to a reference frequency selected according to the receiving channel between 954.38 MHz and 979.38 MHz. Alternatively, if the dual band receiver operates in GPS mode, the VCO 100 is phase locked to a reference frequency of 958.47 MHz such that the frequency of the second harmonic signal component is 1916.94 MHz. As such, since the technology itself for controlling the PLL to oscillate a desired frequency signal in the VCO of the PLL in the mobile communication terminal is conventional, detailed description thereof is omitted.

As described above, the signal output from the VCO 100 is commonly applied to the first and second BPFs 102 and 104. Here, the first BPF 102 uses a BPF having a pass band of fo, and the second BPF 104 uses a BPF having a pass band of 2 fo. Then, the first BPF 102 band-passes the output signal of the VCO 100 and passes only the reference frequency signal fo to apply it to the mixer 106, and the second BPF 104 outputs the output signal of the VCO 100. The bandpass filter is applied to the mixer 108 by passing only the second harmonic signal 2fo of 1916.94MHz.

The first mixer 106 then mixes the RF1 of 824.38 MHz to 849.38 MHz with the reference frequency signal fo of 954.38 MHz to 979.38 MHz passing through the first BPF 102 and uses 85.38 MHz as the IF frequency of the receiver of the CDMA2000. Generates an IF signal. The second mixer 108 also mixes the RF2 at 1575.42 MHz and the second harmonic component signal 2fo at 1916.94 MHz passing through the second BPF 104 to generate a 341.52 MHz signal. The 341.52 MHz signal generated in this manner is four times the frequency of the IF signal used in the receiver of the CDMA2000. Accordingly, the signal of 341.52 MHz is divided into four by the divider circuit 110. That is, the signal of 341.52 MHz is divided into two by the divider 112 and becomes 170.76 MHz, and then divided by the divider 114 and the divided into two by the frequency of 85.38 MHz, which is used as the IF frequency of the receiver of the CDMA2000. Is generated. In this way, the IF signal output from the first mixer 106 or the divider circuit 110 is applied to the IF signal receiving circuit (not shown) and processed.

Therefore, using one VCO set to use for both frequency bands using the harmonic characteristics of VCO, VCO reference frequency signal is used for transmitting and receiving RF signal of existing cellular frequency band or PCS frequency band. It can be used to receive GPS signals with second harmonic components, simplifying circuit configuration.

Meanwhile, in the above description of the present invention, specific embodiments have been described, but various modifications can be made without departing from the scope of the present invention. In particular, the embodiment of the present invention has been shown to be applied to the case of receiving the cellular frequency band or PCS frequency band and the GPS signal, but also applies to the case where the frequency band is different. Therefore, the scope of the invention should not be defined by the described embodiments, but should be defined by the equivalent of claims and claims.

As described above, the present invention uses a single VCO set to be used in both frequency bands by using the harmonic characteristics of the VCO, and by configuring the RF signal receiving circuit of the dual band receiver, the circuit configuration can be easily and simplified. There is an advantage.

Claims (4)

Receiving a high frequency signal for converting a high frequency signal of the first and second frequency bands into an intermediate frequency signal in a dual band receiver for receiving a high frequency signal of a first frequency band and a high frequency signal of a second frequency band higher than the first frequency band In the circuit, A voltage controlled oscillator including an impedance matching circuit set at an output terminal such that a reference frequency signal oscillating as a local oscillation frequency signal corresponding to the first frequency band and an output power level of a second harmonic signal component thereof are similar to each other; A first band pass filter connected to an output terminal of the voltage controlled oscillator and passing only the reference frequency signal; A second band pass filter connected to an output terminal of the voltage controlled oscillator to pass only the second harmonic signal; A first mixer which generates the intermediate frequency signal by mixing the high frequency signal of the first frequency band and the reference frequency signal passing through the first band pass filter; A second mixer for mixing a high frequency signal of the second frequency band and a second harmonic component signal passing through the second bandpass filter to generate a signal that is an integer multiple of the intermediate frequency; And a divider circuit for dividing the output signal of the second mixer to generate the intermediate frequency signal. The high frequency signal receiving circuit according to claim 1, wherein the first frequency band is a cellular frequency band, and the second frequency band is a GPS (Global Positioning System) frequency band. 2. The high frequency signal receiving circuit according to claim 1, wherein the first frequency band is a personal communication service (PCS) frequency band, and the second frequency band is a global positioning system (GPS) frequency band. 4. The high frequency signal receiving circuit according to claim 2 or 3, wherein the frequency divider circuit comprises two two frequency divider circuits connected in cascade.