KR20070048806A - Dual frequency reception of spread spectrum signals - Google Patents

Abstract

The present invention relates to a method, a computer program, a computer program product, a system, a transmitter, a receiver and a module for dual frequency reception, comprising a first signal having a first center frequency and a second signal having a second center frequency. A received signal is obtained, the received signal is processed to produce an output signal, and one or more types of the output signal can be generated, and the first type of output signal is frequency converted to a third center frequency. It is proportional to the sum of the signal and the second signal frequency-converted to the third center frequency. The first and second signals may, for example, be positioning signals in a dual frequency satellite based positioning system.

Description

Dual frequency reception of spread spectrum signals

The present invention relates to a method, a computer program, a computer program product, a receiver and a module for dual frequency reception. The invention further relates to a transmitter in a system of dual frequency reception and the system itself.

Dual frequency reception is particularly relevant to receivers of satellite-based positioning systems such as the Global Positioning System (GPS) and the upcoming Galileo system.

The GPS system uses 24 satellites distributed over six orbits 20,200 km above the earth. Satellites take 12 sidereal hours to orbit the earth.

All GPS satellites emit signals at two frequencies, L1 (1575.42 MHz) and L2 (1227.6 MHz). Three pseudorandom noise (PRN) ranging codes are currently in use:

C/A(coarse/acqusition)코드는 L1 반송파를 변조하는데, 그것은 네비게이션 메시지를 운반하고 1.023MHz 칩레이트 및 1ms의 주기를 가진다.

A coarse / acqusition (C / A) code modulates the L1 carrier, which carries the navigation message and has a 1.023 MHz chip rate and 1 ms period.

P(precision)코드는 L1 및 L2 반송파들을 변조하고 10.23MHz 레이트와 7 일의 주기를 가진다.

The P (precision) code modulates the L1 and L2 carriers and has a 10.23 MHz rate and a period of 7 days.

Y-코드는 현재 P-코드 대신 사용되고 있는데(Y-코드는 P-코드를 허가된 사용자들에게만 알려지는 W-코드로써 부호화하는 것에 의해 얻어진다) 안티-스푸팅(anti-spoofing; A/S)이 1994년 이래 활동하고 있기 때문이다. 상응하는 옵저버블(observable)들은 Y1 및 Y2이다.

Y-code is currently being used instead of P-codes (Y-codes are obtained by encoding P-codes as W-codes known only to authorized users). Anti-spoofing (A / S) ) Has been active since 1994. Corresponding observables are Y1 and Y2.

In the scope of modernization of GPS, new L2C (L2C) signals will be transmitted by modernized IIR (IIR-M) and all subsequent GPS satellites. The L1 and new L2C signals will then be available to citizens (unlicensed users). In addition, the third civil signal L5 will be transmitted on a third carrier of 1176.5 MHz.

GPS receivers may be manually transported or installed in aircraft, ships, tanks, submarines, vehicles and trucks, for example. These receivers detect, decode and process GPS satellite signals. They are locked to signals from four GPS satellites to provide a full three dimensional position.

Different types of receivers are using different parts of the GPS signal structure. The basic observable in the GPS receiver is the C / A-code on the current L1 carrier. These signals allow the GPS receiver to calculate the distances for the four satellites, and use the data to calculate its own position on the earth's latitude and longitude within +/- 100 meters and 95% of the viewpoint. Since the four signals received are stabilized by an atomic clock, the timing accuracy of a normal digital clock is sufficient for the calculations made in the GPS receiver unit. This is achieved by the low quality digital clock used by the GPS receiver by taking advantage of the fact that only three satellite signals are actually required to determine the position of the GPS receiver and by using the additional degrees of freedom represented by the fourth received satellite signal. This is accomplished by correcting the timing errors caused.

When the GPS receiver receives the PRN code from the satellite, it generates a plurality of duplicate codes and correlates the received PRN code with the plurality of duplicate codes. Duplicate codes that achieve the best correlation identify the transmitting satellite and multiply the speed of the light by the time interval that must be shifted at the receiver to maintain maximum correlation with the received PRN code. same. The corresponding position of the satellite can be extracted from the almanac implemented in the GPS receiver. The satellite range is called pseudo range because the measurement must be modified by various factors to get the true range. Modifications that must be applied include signal propagation delays caused by ionospheric and convective layers, satellite clock errors, and GPS receiver clock errors. The true geographical distance for each satellite is obtained by applying these corrections to the measured pseudo range.

By using dual frequency phase measurements and knowledge of the inverse square relationship between the frequency and the group delay of each carrier (eg, L1 and L2), a simple linear correction of the delay caused by the ionosphere is derived. This modification can be expressed as:

Where τ _L1 is the ionospheric delay for carrier L1 and Δτ _{L1 , L2} is the difference in delay between L1 and L2.

In order to increase the accuracy of satellite based positioning, the GPS receiver must receive both L1 and L2 carriers (or other combinations of future L1, L2 and L5, for example L2 and L5), Complete receiver structures require implementation in the GPS receiver, thus increasing both the size and cost of the GPS receiver.

To alleviate this problem, US 6,675,003 B1 proposes a mixer structure capable of frequency converting both L1 and L2 signals. To this end, the received L1 signal is frequency-converted to the first intermediate frequency, and the received L2 signal is frequency-converted to the second intermediate frequency IF. The resulting IF signals are simultaneously frequency-converted to the final IF with a single image reject (IR) mixer using a mixer frequency that is roughly between the first and second IFs. The IR mixer generates the L1 signal converted into the final IF to the first output and the L2 signal converted into the final IF to the second output, or the L1 signal converted to the final IF and the final IF. It is possible to switch between L2 signals, which are output through a single output of the IR mixer.

However, the mixer structure proposed in US Pat. No. 6,675,003 B1 still requires two mixers for radio frequency (RF) to IF conversion and, moreover, shows a more complex architecture to achieve switching.

In view of the above problems, the present invention proposes a method, computer program, computer program product, system, transmitter, receiver and module for efficient dual frequency reception.

Obtaining a received signal containing a first signal having a first center frequency f ₁ and a second signal having a second center frequency f ₂ , and processing the received signal to generate an output signal; , and the output signal of one or more types may be generated, the output signal of the first type, the third center frequency (f ₃₎ to the frequency-converted first signal and the frequency to the third center frequency (f ₃₎ A method for dual frequency reception comprising a proportional to the sum of the converted second signal is proposed.

The received signal has been transmitted by one or several transmitters and received at the receiver. The received signal contains a first signal having a first center frequency and a second signal having a second center frequency and can therefore be regarded as a dual frequency signal. The signals may be, for example, modulated and possibly spread information carrier symbols, and the center frequency may be, for example, the frequency of the modulation carrier. For example, the first and second signals may be two of three signals transmitted respectively on L1, L2 and L5 carriers of a global positioning system (GPS), the first and second signals being one It was sent by the transmitter (satellite) of. Equally, the first and second signals may be generated by satellites of other transmitters (satellites), for example other positioning systems such as GPS and Galileo. Regardless of their origin, from the receiver's point of view, the first and second signals are superimposed on the received signal obtained by the receiver.

To obtain the received signal, the receiver may deploy one or more antennas, for example a dual frequency antenna, or two separate antennas, each tuned to the frequency of the first and second signals. The acquiring of the received signal includes filtering of signals received by at least one antenna and, if receiving and / or filtering is performed at two branches of the receiver, containing the first and second signals. A combination of signals of both branches to obtain the received signal may be required.

The received signal may be subjected to further processing to generate an output signal from which one or more types of output signals may be generated. Which type of output signals are actually generated may be adaptively determined by the receiver based on, for example, the characteristics of the received signal and the first and second signals contained therein.

The output signal of the first type in the at least one type that can be generated is the third center frequency (f ₃₎ to the frequency-converted first signal and the third center frequency (f ₃₎ frequency converting the second signal to Is proportional to the sum of The signals are frequency converted by shifting the center frequencies of the signals. The first center frequency f ₁ of the first signal is shifted to the third center frequency f ₃ , and correspondingly, the second center frequency f ₂ of the second signal is the third center frequency (f ₁ ). f ₃ ). The frequency conversion may be achieved by a mixer, for example, and it may be possible to up-convert, ie shift the center frequency to a higher frequency and down-convert, ie shift the center frequency to a lower frequency.

According to an embodiment of the invention, the dual frequency reception signal is the second signal of the second to the third center frequency (f ₃₎ with a frequency conversion of the first signal and the third center frequency (f ₃₎ the frequency conversion Proportional to the sum. When frequency converting the first and second signal components, it is allowed to superimpose both of the frequency converted signals on the output signal, which makes the structure of the mixer performing the frequency conversion extremely simple. For example, the mixer may consist of only a local oscillator that generates a sinusoidal frequency that is multiplied by the received signal containing the first and second signals. Spread spectrum in which the characteristics of the first and second signals, for example the signals are spread with other spreading codes, for detecting and / or recovering frequency-converted first and second signals superimposed on the output signal The property of signals can be used. In order to perform this detection and / or recovery, the output signal if the third center frequency f3, in which the superposition of the first and second signals is frequency-converted, does not already serve as a baseband frequency. It may be required to further frequency convert P to baseband frequency.

Therefore, according to an embodiment of the present invention, at least two types of output signals may be generated, and the output signal of the second type is substantially the first signal frequency-converted to the third central frequency f ₃ , And the second signal frequency-converted to the third center frequency f ₃ .

This embodiment makes it possible to select between two output signals, wherein the output signal of the first type is the first signal and the third center frequency f ₃ which are frequency-converted into the third center frequency f _3. The output signal of the second type is substantially the first signal frequency-converted to the third center frequency f ₃ , or substantially the third center. The second signal is frequency converted to a frequency f ₃ . It is then possible to choose between dual frequency reception in which the two signals are present in the output signal, or single frequency reception in which only one of the two signals is present in the output signal. At that point, the output signal of the second type and the third center frequency (f ₃₎ to the frequency-converted first signal or both the third center frequency (f ₃₎ to be the second signal frequency-converted It is additionally possible to choose whether it can.

According to an embodiment of the present invention, said processing for generating said output signal of said first type multiplies said received signal with a sine wave having a fourth center frequency f ₄ to obtain said output signal of said first type. Steps. The sinusoidal wave may be, for example, a cosine function having a polarization angle 2πf ₄ . The fourth center frequency f ₄ may be selected depending on the first and second center frequencies, for example. Obviously, this embodiment of the present invention enables an extremely simple setup of frequency conversion of both the first and second signals.

According to an embodiment of the present invention, f ₁ ≥ f ₂ , f ₄ = f ₂ + (f ₁ -f ₂ ) / 2 and f ₃ = f ₁ -f ₄ are maintained. In this case, a fourth center frequency f ₄ is located between the first and second center frequencies so that when the received signal is multiplied with the sinusoidal wave having the fourth center frequency f ₄ , Overlapping occurs at the third center frequency f ₃ = f ₁ -f ₄ of the first signal and the second signal.

According to an embodiment of the present invention, the processing of generating the output signal of the second type comprises the steps of: multiplying the received signal by a first sinusoidal wave having a fourth center frequency f ₄ to obtain a first mixed signal; And multiplying the received signal by a second sinusoidal wave to obtain a second mixed signal, wherein the second sinusoidal wave has the same center frequency f ₄ as that of the first sinusoidal wave and has a first phase shift from the first sinusoidal wave. another phase shift, phase shifting one of the first and second mixed signals with a second phase shift to obtain a phase shifted mixed signal, and combining the phase shifted mixed signal with the other mixed signal. Obtaining the output signal of the second type.

Depending on the selection of the fourth center frequency f ₄ , the selection of the first and second phase shifts and the manner in which the phase shifted mixed signal and the other mixed signal are combined, the first signal or substantially As a result, the second signal may be frequency-converted to the third central frequency f ₃ .

This embodiment of the present invention is particularly useful because a first step of mixing a received signal with a first sinusoidal wave is necessary for both the generation of the output signal of the first type and the generation of the output signal of the second type. Due to this, its implementation allows a structure suitable for the generation of both first and second types of output signals, and also, for the second type of output signal, frequency conversion to the third center frequency f ₃ . This is because it allows the selective generation of the first or second signal substantially as an output signal of the second type. For this purpose, this transition must be provided to the corresponding control arrangement which sets the phase shifts and signs of the combinations and sets the tap of the desired first or second type of output signal at the correct position of the transition.

According to an embodiment of the present invention, f ₁ ≥ f ₂ , f ₄ = f ₂ + (f ₁ -f ₂ ) / 2 and f ₃ = f ₁ -f ₄ are maintained. In this case, the fourth center frequency f ₄ is located between the first and second center frequencies. Then, if the first phase shift is −π / 2 (eg, the sine wave is cosine and the second sinusoid is sine), then the second phase shift is π / 2 and the first If applied to a mixed signal, and if the phase shifted mixed signal and the other signal are combined by adding the phase shifted mixed signal and the other signal, substantially only the frequency-converted representation of the first signal It is possible to exist at the third center frequency f ₃ . By changing the first and / or second phase shift, and / or by changing the mixed signals to which the second phase shift is applied, and / or of the phase shifted mixed signal and the other mixed signal. By changing the signs of the combination, it can be achieved that substantially only the frequency converted representation of the second signal is present at the third center frequency f ₃ . Due to incomplete transitions and incomplete timing, it is inevitable that strongly attenuated components of the first signal are present at the third center frequency f ₃ , so that only "substantially" a frequency-converted representation of the second signal is It is present at the third center frequency f ₃ .

According to an embodiment of the present invention, the phase shift is π / 2.

According to an embodiment of the present invention, the phase shift is ± π / 2.

According to an embodiment of the present invention, the phase shifted mixed signal and the other mixed signal are combined by one of addition and subtraction.

According to an embodiment of the present invention, the output signal of the second type is substantially the first signal frequency-converted to the third central frequency f ₃ , and the quality of the first signal is determined, Which of the at least two types of the output signal is produced as an output signal is determined at least in part depending on the determined quality.

The quality of the first signal can be, for example, a signal-to-noise ratio, or a signal-to-noise and interference ratio, or a power level, or any other measurand related to the characteristics of the first signal. The quality of the first signal contained in the received signal may be determined, for example, by separating the first signal from the received signal by filtering and subsequently examining the filtered received signal.

This embodiment is characterized in that if the first signal is regarded as a main signal, if the second signal is regarded as an auxiliary signal, and if it is frequency converted from the output signal to the third center frequency f ₃ If the sum of the first and second signals at a time causes degradation of the first signal for later processing, for example, incomplete separation of the first and second signals from the output signal may result in some noise. Is particularly advantageous because it adds to the first signal. It is reasonable to determine if the first (main) signal can withstand the deterioration of its quality and still be used for further processing, or if this deterioration is unacceptable depending on the determined quality of the first signal. It can be said. This determination may be based on a comparison of the determined quality with a threshold that may be fixed or adaptively determined. If the determined quality is quite sufficient, the output signal of the first type can be selected for generation, and then, in addition to the first (main) signal, the second (auxiliary) signal can also be processed. In a GPS system, for example, the first signal may be an L1 signal, the second signal may be an L2 signal, and if the quality of the L1 signal is sufficiently sufficient, dual frequency reception of L1 and L2 signals may be performed. (Output signal of the first type), so that an increased accuracy of positioning is achieved. On the other hand, if the quality of the L1 signal is found to be insufficient, only the L1 signal is received so as not to further degrade the quality of the L1 signal by incomplete separation from the L2 signal (type 2 output signal).

According to an embodiment of the invention, the output signal of the first type is generated if the determined quality is higher than a threshold. This value may be fixed or adaptively determined.

According to an embodiment of the present invention, the processing for generating an output signal is performed by a mixer for frequency converting an input signal to an intermediate frequency f _IF by a frequency difference f _LO and for the frequency down-converted input signal. Controlled to reduce the influence of the video signal, the video signal has the same center frequency as one of f _LO -f _IF and f _LO + f _IF .

The mixer may be an image reject mixer, for example, which performs a frequency conversion of the input signal to an intermediate frequency (f _IF ) and contains the image contained in the input signal at frequencies f _LO − f _IF and f _LO + f _IF . Reduce or completely suppress the signal. In this embodiment of the present invention, the image reject mixer can be modified to be controllable, so that the reduction or suppression of the image signal can be turned on or off.

According to an embodiment of the invention, the received signal is used as an input signal to the mixer, f ₁ ≥ f ₂ , f _LO = f ₂ + (f ₁ -f ₂ ) / 2 and f _IF = f ₃ = f ₁ -f _LO , the output signal of the first type is generated by controlling the mixer so as not to reduce the influence of the video signal on the frequency down-converted input signal, The output signal is generated by controlling the mixer to reduce the influence of the video signal on the frequency down converted input signal.

The received signal containing the first and second signals is used as an input signal of the image reject mixer, and the mixer frequency f _LO is centered between the first center frequency f ₁ and the first center frequency f ₂ . Is selected to be located. Then, for the first signal, the second signal represents the video signal, and similarly for the second signal, the first signal represents the video signal.

If the image reject mixer of the mixer is turned off, the received signal is multiplied by a cosine having a center frequency f _LO to frequency convert the first signal to the intermediate frequency (or third frequency) f _IF = f ₃ . Also, by converting the second signal to the intermediate frequency f _IF , two signals are suppressed in the output signal.

If the video rejection is turned on, and if the video rejection is controlled to reduce or suppress the rejection signal, then the first branch of the video rejection mixer is the same as the output signal in the above case where no video rejection is performed. The second branch of the image reject mixer, when generating a signal, is added to the first branch of the signal to obtain the output signal, reducing the frequency-converted version of the second signal at an intermediate frequency f _IF , or Produces a suppressive signal, so that the output signal contains substantially only the first signal that is frequency converted to an intermediate frequency f _IF . Similarly, the image reject mixer may be controlled to reduce or suppress the first signal, and when the image rejection is turned on, the output signal is substantially frequency-converted to the intermediate frequency f _IF . Contains only signals.

This embodiment of the present invention can be controlled to select if the same video reject mixer can be used to generate both types of output signal and if any of the first and second signals are regarded as video signals to be reduced and suppressed. It is particularly useful if it is possible to also select between two alternatives of the output signal of the second type.

According to embodiments of the present invention, the frequency difference f _LO is tunable. This is particularly useful if dual frequency reception of signals that do not always have the same center frequencies is desired. For example, in one situation, dual frequency reception of L1 and L2 signals of a GPS system having center frequencies of 1575.4 MHz and 1227.6 MHz, respectively, may be desired, and in other situations,

All. Dual frequency reception of a L1 signal of a GPS system having a center frequency of 1575.4 MHz and a signal from a Galileo system having a center frequency different from 1227.6 MHz may be desired. With respect to the mixer frequency f _LO , which is located in the center of the two center frequencies of the signals to be received in accordance with the invention, it is necessary for the f _LO to vary in a certain range.

According to an embodiment of the present invention, the obtaining of the received signal comprises: receiving a signal containing the first and second signals as a first antenna to obtain a first received signal, wherein the first antenna At least partially fitting the first signal, receiving a signal containing the first and second signals as a second antenna to obtain a second received signal, wherein the second antenna is configured to receive the second signal. At least partially fitting the first received signal to a first filter structure adapted to at least partially fit the first signal to obtain a first filtered signal; Filtering with a second filter structure that is at least partially adapted to the second signal to obtain a second filtered signal; and combining the first and second filtered signals to receive the received signal. Obtaining steps. The antennas may be tuned to have a reception maximum at the center frequencies of the individual signals, for example, and the filter structures may have a passband greater than or equal to the bandwidth of the individual signals and other stopbands for noise and interference suppression. can be designed to have a stop-band).

According to an embodiment of the invention, the first filter structure comprises a bandpass filter, and the second filter structure comprises a combination of lowpass and highpass filters. The quality of the combination of lowpass and highpass filters may be lower than the quality of the bandpass filter, but the combination may be cheaper than the single filter and the quality of the first and / or second signals is in some way high. May be sufficient for the filtering of signals that are only considered.

According to an embodiment of the present invention, the obtaining of the received signal comprises: receiving a signal containing the first and second signals with a dual frequency antenna to obtain a received signal, and receiving the received signal from the first Filtering with a first filter structure at least partially adapted to the signal to obtain a first filtered signal; filtering the received signal with a second filter structure at least partially adapted to the second signal; Obtaining the received signal, and combining the first and second filtered signals to obtain the received signal.

According to an embodiment of the invention, the output signal is frequency converted to a baseband center frequency. The baseband center frequency is significantly less than the third center frequency f ₃ . The frequency conversion to the baseband center frequency makes it possible to detect the first and / or second signal and / or to reconstruct information contained in the first and / or second signal.

According to an embodiment of the present invention, the first and second signals are spread spectrum signals which are respectively spread with different spreading codes. The spreading codes are chips, for example ones and zeros or positive and negative sequences, each having a fixed chip duration, the chip duration of the chips being spread It is much smaller than the duration of the information carrier symbol. Spreading may be accomplished by multiplying information carrier symbols by a sequence of chips to increase the bandwidth (spectrum) of the spreading symbols, which may be marked as spreading spectrum signals. If two different spreading codes are used to spread two different sequences of information carrying symbols, the two obtained spread spectrum signals are orthogonal or pseudo-orthogonal to each other depending on the cross-correlation properties of the spreading codes used. pseudo-orthogonal). It is then possible to recover two sequences of information carrier symbols from the sum signal by adding both spread spectrum signals and despreading with the corresponding spread code, the despreading being code-matched filtering, ie sum This is accomplished by multiplying the signal with one of the spreading codes and integrating the obtained sequence of chips over periods corresponding to the symbol duration. In a GPS system, for example, all three signals L1, L2 / L2C and L5 are spread spectrum signals each spread with different spreading codes. The same holds for the signals used in the Galileo system.

According to an embodiment of the invention, the output signal is converted to a baseband center frequency to obtain a baseband signal, wherein the first and second signals are correlated with their corresponding spreading codes by the baseband signal. Is detected. At the baseband center frequency at which the output signal is to be frequency-converted, for example by an additional mixer, superimposed first and second signals during frequency conversion by the correlation to the third center frequency f ₃ It is possible to detect. The quality of the detection depends on the cross-correlation properties of the codes that were used to spread the spread spectrum signals. It is then possible to recover the contents of the first and / or second signal from the baseband signal by despreading.

According to an embodiment of the invention, the first and second signals are transmitted to the receiver by at least one transmitter of at least one satellite based positioning system. The transmitter may for example be a satellite. The first and second signals may be transmitted by the same transmitter of the same positioning system, by other transmitters of the same positioning system, or by other transmitters of other positioning systems.

According to an embodiment of the invention, said at least one satellite based positioning system comprises at least one of a global positioning system and a Galileo system.

According to an embodiment of the invention, the first frequency f ₁ is 1575.4 MHz and the second frequency f ₂ is in the range between 1176 and 1227 MHz. This allows the reception of the L1 signal of the GPS system and one of the L2 signal of the GPS system and the signals of the Galileo system.

Further proposed is a computer program having instructions that enable a processor to control a receiver that performs the aforementioned method steps.

In addition, a computer program product is proposed that includes a computer program having instructions that allow a processor to control a receiver that performs the foregoing method steps.

As at least one transmitter, and at least one system for storing and transmitting the signal to a receiver, the at least one transmitter, first center frequency the first signal and the second center frequency (f ₂₎ having a (f ₁₎ Means for transmitting a signal containing a second signal, wherein the at least one receiver comprises: means configured to obtain a received signal containing the first and second signals; Means for generating an output signal, wherein said output signal of one or more types may be generated, said output signal of a first type being said first signal and said third signal frequency-converted to a third center frequency f ₃ ; Further proposed is a system comprising means proportional to the sum of the second signal frequency converted to a center frequency f ₃ .

The system may for example be a GPS system and a Galileo system.

A transmitter of a system for transmitting signals, comprising: means configured to transmit a signal containing a first signal having a first center frequency and a second signal having a second center frequency, the first and second signals Are received by at least one receiver, the received signal is processed at the at least one receiver to produce an output signal, and one or more types of the output signal can be generated, the first type of the output signal is the third center frequency (f ₃₎ to the frequency-converted first signal and the third center frequency (f ₃₎ to the transmitter proportional to the sum of the second signal frequency converter are added proposed to.

The transmitter may be, for example, a satellite in a satellite-based positioning system, such as a GPS or Galileo system.

A receiver for dual frequency reception, comprising: first means configured to obtain a received signal containing a first signal having a first center frequency f ₁ and a second signal having a second center frequency f ₂ , and A second means configured to process said received signal to generate an output signal, said output signal of one or more types being capable of being frequency-converted to a third center frequency f ₃ ; There is further provided a receiver comprising second means proportional to the sum of the first signal and the second signal frequency-converted to the third central frequency f ₃ .

According to an embodiment of the present invention, the second means comprises: means for multiplying the received signal by a sine wave having a fourth center frequency f ₄ to obtain a first mixed signal, and the first mixed signal by the first mixed signal. Means for outputting as said output signal of a tangible type.

According to an embodiment of the present invention, at least two types of output signals may be generated, and the output signal of the second type is substantially the first signal and the frequency converted to the third central frequency f ₃ . One of the second signals frequency-converted to a third center frequency f ₃ , and the second means multiplies the received signal with a sine wave having a fourth center frequency f ₄ to obtain a first mixed signal. Means configured to multiply the received signal with a second sinusoid to obtain a second mixed signal, wherein the second sinusoid has a center frequency f ₄ equal to the first sinusoid and has the first sinusoidal wave; Means for differentiating a first phase piece by means of phase shifting one of said first and second mixed signals to obtain a phase shifted mixed signal, said phase shifted mixed signal and said other mixed signal Combined Means arranged to obtain a call, and means configured to output, as the output signal of the second type of the combined signal.

According to an embodiment of the present invention, at least two types of output signals may be generated, wherein the output signal of the second type is the first signal frequency-converted to the third center frequency f ₃ , and the receiver Means further comprises means configured to determine the quality of the first signal, and means configured to determine at least in part depending on the determined quality whether the output signal of any of the at least two types is generated as an output signal. .

According to an embodiment of the present invention, the second means converts an input signal into an intermediate frequency f _IF by a frequency difference f _LO and reduces an influence of an image signal on the frequency down-converted input signal. A mixer that can be controlled, the video signal includes a mixer having the same center frequency as one of f _LO -f _IF and f _LO + f _IF .

According to an embodiment of the invention, the second means further comprises means configured to input the received signal to the mixer.

According to an embodiment of the invention, the first means is a first antenna for receiving a signal containing the first and second signals to obtain a first received signal, and at least partially adapted to the first signal. A first antenna adapted to receive a signal containing the first and second signals to obtain a second received signal, the second antenna being at least partially adapted to the second signal, A first filter structure for filtering the first received signal to obtain a first filtered signal, the first filter structure being at least partially adapted to the first signal, and filtering the second received signal for a second A second filter structure for obtaining a filtered signal, comprising: a second filter structure adapted to be at least partially suitable for the second signal, and combining the first and second filtered signals to obtain the received signal. It comprises a means.

According to an embodiment of the invention, the first filter structure comprises a bandpass filter, and the second filter structure comprises a combination of lowpass and highpass filters.

According to an embodiment of the invention, the first means is a dual frequency antenna for receiving a signal containing the first and second signals to obtain a received signal, the first signal by filtering the received signal A first filter structure for obtaining a first filter structure, the first filter structure being at least partially adapted to the first signal, and a second filter structure for filtering the received signal to obtain a second filtered signal. A second filter structure that is at least partially adapted, and means configured to combine the first and second filtered signals to obtain the received signal.

According to an embodiment of the present invention, the first and second signals are spread spectrum signals that are respectively spread with different spreading codes, and the receiver frequency-converts the output signal to a baseband center frequency to obtain a baseband signal. Means configured to detect the first and second signals in the baseband signal by correlation with their corresponding spreading codes.

In a module for dual frequency reception at a receiver, the module obtains a received signal containing a first signal having a first center frequency f ₁ and a second signal having a second center frequency f ₂ . First means configured to comprise; And second means configured to process the received signal to generate an output signal, the output signal being of one or more types, wherein the output signal of the first type is frequency converted to a third center frequency f ₃ . Further proposed is a module comprising second means proportional to the sum of the first signal and the second signal frequency-converted to the third central frequency f ₃ .

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described below.

1 shows a schematic diagram of a satellite based positioning system according to an embodiment of the present invention;

2 shows a schematic diagram of radio frequency (RF) and intermediate frequency (IF) sections of a receiver according to an embodiment of the invention;

3A shows a schematic diagram of the frequency spectrum of a mixer input signal according to an embodiment of the present invention;

3B shows a schematic diagram of the frequency spectrum of the mixer output signal when image rejection is turned off in accordance with an embodiment of the present invention;

3C shows a schematic diagram of the frequency spectrum of the mixer output signal when image rejection is turned on in accordance with an embodiment of the present invention; And

4 shows an exemplary flow chart of a method for dual frequency reception according to an embodiment of the present invention.

As an initial note, it should be noted that the subject matter of the introduction of this patent specification can be used to support this detailed description.

The present invention proposes to provide a controllable video rejection mixer with a received signal containing first and second signals, wherein the mixer frequency of the controllable video rejection mixer is between the center frequencies of the first and second mixers. The video rejection capability of the selectable and controllable video rejection mixer can be controlled. This produces an output signal that is proportional to the sum of the first and second signals frequency-converted to an intermediate frequency or substantially only one of the first and second signals frequency-converted to the intermediate frequency. Makes it possible to generate In the former case, signal characteristics, such as, for example, that the first and second signals are spread spectrum signals, are used to detect and / or recover the first and second signals from the sum signal.

1 schematically depicts a satellite-based positioning system 1, in which a plurality of satellites 2-1, ... 2-3 transmits positioning signals to a receiver 3, said positioning signal. Each of these contains first and second signals having first and second center frequencies, respectively, wherein the first and second signals are spread spectrum signals. For each satellite 2-1,... 2-3 which the receiver 3 can receive its signals, for example for satellite 2-1, the receiver 3 Receives a received signal containing the first and second signals transmitted by the satellite 2-1, and processes the received signal to determine the identity of the satellite and the distance to the satellite 2-1. . Based on the identity of the satellite, the receiver can determine the position of the satellite, and if the distance and position of at least three satellites are determined by the receiver 3, it is possible to determine the position of the receiver using the triangular method. . The reception of the signals of the fourth satellite can be used to catch timing errors originating from the digital clock used in the receiver 3. The detection of the first signal transmitted by each of the satellites may be sufficient to determine the position of the receiver, wherein additional reception of the second signal is caused by, for example, an ionospheric signal and if transmitted at dual frequencies Can be used to increase the accuracy of positioning by eliminating the propagation delay that can be determined if it becomes available to the receiver 3.

The satellites 2-1, ..., 2-3 may for example be satellites of a global positioning system (GPS) or a Galileo system, and the receiver 3 is transmitted simultaneously by the satellites of both systems. Receive and process signals. For example, the receiver 3 may receive a first signal having a first center frequency of the satellite 2-1 operated according to the GPS, and at the same time the satellite 2-2 operated according to the Galileo system. A second signal having a second center frequency of may be received.

Figure 2 schematically depicts an architecture 4 comprising a radio frequency (RF) section, also referred to as the front end of a dual frequency receiver, and an intermediate frequency (IF) section according to an embodiment of the invention. The architecture can be encapsulated equally well into a module, where the module, possibly with additional components, is integrated or connected to a receiver, for example a mobile phone or a laptop, to allow dual frequency reception therein.

The architecture 4 comprises a dual frequency antenna 6 for receiving a received signal comprising first and second signals, a band pass filter 7 for filtering the received signal to separate the first signal, and filtering the received signal. A combination of a high pass filter 8 and a low pass filter 9 for separating the second signal, an adder 10 for combining the two filtered signals, an amplifier 11 for amplifying the sum signal, and control And a controllable video rejection mixer 5, wherein the controllable video rejection mixer 5 frequency down-converts the first and / or second signals contained in the mixer input signal at the output of the amplifier 11; And generate a mixer output signal at the output of the image reject mixer 5, which can then be converted to baseband (BB) frequency and further processed (not shown in FIG. 2).

The present invention is based on the idea of down converting a first signal having a first center frequency, which is also represented as a first channel, and a second signal having a second center frequency, which is also displayed as a second channel, overlapping each other. Since all GPS L1, L2 and L5 and Galileo satellite signals transmitted at different frequencies are spread to different spreading codes, it is possible to detect the first and second signals even if they are down converted to the same frequency. . The cross-correlation properties of these codes allow the performance of the two aligned signals to be as good as using individual signals.

Down conversion of the two channels is done in a manner that minimizes the need for extra hardware. This is obtained by using the down conversion mixer 5 in the case of proceeding as expected in the single carrier reception mode with the image frequency cancellation characteristic, and this image rejection is turned off when trying to receive two carriers.

The internal structure of the image reject mixer 5 is actually generated by the local oscillator 52 and, if applicable, two multipliers 50-1 and 50 fed with sinusoids whose phase is shifted by an instance 51. -2), phase shifter 53 and coupling portion 54. Among them, multiplier 50-1 can be controlled by switch 55, for example by separating itself from its bias current Vcc.

The controllable image rejection mixer 5 functions as follows:

The first and second signals are

및

And

Each is displayed as follows. If the local oscillator produces a cosine with frequency f ₄ = f ₂ + (f ₁ -f ₂ ) / 2 and if the instance 51 adds a phase shift to the signal supplied to the multiplier 50-1 If a phase shift of -π / 2 is added to the signal supplied to the multiplier 50-2 (then it becomes a sine), the signal I ₁ (t) at the output of the multiplier 50-1 is Can be expressed as:

Signal I ₂ (t) at the output of multiplier 50-2 can be expressed as follows:

The signal I ₃ (t) at the output of the phase shifter 53 (phase shift π / 2) can then be expressed as:

.

.

Now consider three situations:

는 그러면 다음과 같이 주어지는데,a) The switch 55 is turned off and image rejection is not performed. Output signal of controllable video rejection mixer 5

Is then given by

That is, the first and second signals are shifted to the frequency f ₃ = f ₁ -f ₄ = f ₄ -f ₂ , summed and attenuated by 3 dB.

는 다음과 같이 주어지는데b) the switch 55 is turned on and, the image rejection is performed, and (phase shifter 53) of the signal at the output at the output) of the signal I ₃ (t) and (a multiplier (50-2) ₂ I (t) is combined by addition in the coupling circuit 54. Then the output signal of the controllable video rejection mixer 5

Is given by

That is, the first signal is shifted to the frequency f ₃ = f ₁ -f ₄ and the second signal is suppressed.

는 다음과 같이 주어지는데c) switch 55 is turned on and, the image rejection is performed, and (phase shifter 53) of the signal at the output at the output) of the signal I ₃ (t) and (a multiplier (50-2) ₂ I (t) is combined by subtracting I ₃ (t) from I ₂ (t) in the coupling circuit 54. Then the output signal of the controllable video rejection mixer 5

Is given by

That is, the second signal was shifted to the frequency f ₃ = f ₄ -f ₂ , and the first signal was suppressed.

The output signal of the mixer according to situation 3) may be achieved by summing I ₃ (t) and I ₂ (t) and using a phase shift of −π / 2 in the phase shifter 53. As long as the phase shifter instance 51, phase shifter 53, and coupling unit 54 are properly configured, the desired image rejection is when the phase shifter 53 is located in the lower branch of the mixer 56 or the phase shifter instance. Other phase shifts of 51 may be achieved when used.

In practical use, image rejection as performed in situations b) and c) above cannot be fully achieved because of the imperfection of the image rejection mixer 5. However, image rejection of the first or second signal of about 20 ... 40 dB can be achieved. Since the first and second signals are transmitted with a relative power level difference of only two dBs, this image rejection is still performance during exclusive reception of the first signal (situation b)) or exclusive reception of the second signal (situation c)). Large enough to not cause deterioration.

This is considered in FIGS. 3A-3C, in which the frequency spectra S ₁ and S _{2 of} the first and second signals having center frequencies f ₁ and f ₂ , respectively, are between the two frequencies. It is depicted with the local oscillator frequency f ₄ = f ₂ + (f ₁ -f ₂ ) / 2 set. FIG. 3B illustrates a situation in which mixing of the first and second signals is performed without image rejection and both spectra S ₁ and S ₂ are shifted toward the intermediate frequency f ₃ and attenuated by 3 dB to overlap and attenuate by 3 dB. Is depicted as indicated by the cross hatch. Finally, FIG. 3C shows that the mixing of the first and second signals is performed with image rejection and both spectra S ₁ and S ₂ are shifted toward the intermediate frequency f _{3 while} the spectrum of the second signal is rejected. It describes the situation b) in the case of attenuation by a factor (a) of 20 ... 40 dB.

According to an embodiment of the invention, when dual frequency reception of both the first and second signals is required, the image rejection is turned off by the switch 55 (situation a). This means that multiplier 50-1 is turned off by shutting down bias current Vcc. Alternatively, the other components of the multiplier or the entire upper branch of the controllable image reject mixer 5 may be switched off. Among them, the first alternative of shutting down the bias current may be the most plausible approach. The controllable video rejection mixer 5 then operates as a normal mixer which never has video rejection. This means that the first and second signals overlap each other and are down-converted, that is, the first signal lies on top of the second signal or vice versa. In this case, the local oscillator frequency is f ₄ = f ₂ + (f ₁ -f ₂ ) / 2 so that the intermediate frequency is f ₃ = f ₁ -f ₄ = f ₄ -f ₂ .

If the first and second signals are for example L1 and L2 band signals of GPS having center frequencies f ₁ = 1575.4 MHz and f ₂ = 1227 MHz, respectively, then the local oscillator frequency is f ₄ = 1401.5 MHz, resulting in Typical intermediate frequency is f ₃ = 174 MHz.

The intermediate frequency f ₃ at the output of the mixer 5 can then be shifted to the baseband (frequency of approximately zero) by digital means or using another down conversion mixer stage.

If any other signal (e.g., L5 signal) is used as the second signal, or if the frequency of the second signal is changed, the frequency of the local oscillator in the controllable rejection mixer 5 should match the new frequency. can be changed.

For example, to cover all GPS and Galileo signals, the tuning range of this local oscillator can be from 1375 MHz to 1401.5 MHz.

The front-end structure of the architecture 4 of FIG. 2 consists of two branches, the first branch comprising the bandpass filter 7 can be considered as the main branch and the high pass filter 8 and the low pass filter. The second branch comprising (9) can be regarded as a secondary branch. This may be due, for example, to the fact that the first signal filtered at the main branch is transmitted at a higher power level than the second signal filtered at the secondary branch. Note that instead of a dual frequency antenna, separate antennas for each of the two branches are used and it is also possible that these separate antennas can be tuned to the center frequencies of the first and second signals respectively.

If dual frequency reception of both the first and second signals is only required from time to time, for example because the information in the first signal is deemed sufficient for positioning and the second signal may only be required in some cases. It may be beneficial to switch between dual frequency reception and single frequency reception, since This means that incomplete separation of the first signal from the sum of the first and second signals output by the mixer 5 and then converted to baseband when performing dual frequency reception results in a signal-to-noise ratio of the first signal. This is because the SNR decreases. If the SNR of the first signal is already at the sensitivity level, it is beneficial to avoid dual frequency reception. If it is found that the SNR of the first signal is very sufficient to withstand some degradation due to the incomplete separation of the second signal at baseband, dual frequency reception may be performed. The SNR of the first signal can be measured or estimated at the main branch, for example. The front-end filtering on the secondary branch may be designed to consist of only the low pass filter 9 and the high pass filter 8. This is due to the fact that the sensitivity of the secondary branch may not be the most important since the secondary branch is used only in high SNR situations. In the case of GPS and Galileo systems, the frequency response of the secondary branch filter may have a passband of 1170 MHz to 1235 MHz.

The situation in which the first signal becomes more important than the second signal is encountered in the GPS system in which the L1 band signal is transmitted at a higher transmission power than the L2 band signal, for example. According to an embodiment of the present invention, there is an advantage in that dual frequency reception is performed only if the L1 band signal exceeds the sensitivity level of the receiver. Dual frequency reception can be used to determine the propagation delay caused by the ionosphere and thus increase the accuracy of the pseudo ranges. In particular, if the propagation delay caused by the ionosphere only changes slowly in time, too frequent measurements of this amount may not be required in any way.

4 shows an exemplary flow chart of a method for dual frequency reception according to an embodiment of the present invention.

In a first step 400, a received signal is obtained by a receiver, which contains first and second signals having different center frequencies. This may be achieved for example via dual frequency reception or two separate antennas and corresponding filter structures. In a second step 401, the SNR of the first signal is determined, for example, in the main branch of the front-end of the receiver. If it is checked in step 402 that this SNR is greater than the sensitivity threshold, the state variable DualFreqRecept is set to "true" and the mixer's image rejection capability is turned off, so that both the first and second signals overlap the intermediate frequencies. Mixing of the received signal using the controllable video rejection mixer according to the embodiment of the present invention is performed. Otherwise, the state variable DualFreqRecept is set to "false", and the image rejection capability of the mixer is turned on, so that the controllable image rejection according to the embodiment of the present invention is substantially frequency-converted to only the first signal. Mixing of the received signal using a mixer is performed.

Regardless of the output of the check in step 402, the intermediate frequency signal, which is the output by the mixer, is converted to baseband in step 407, resulting in a baseband signal. Depending on the state of the state variable DualFreqRecept checked in step 408, baseband signal processing is performed on the baseband signal. If DualFreqRecept is true, both the first and second signals are detected in the baseband signal by correlation in step 409. In step 410, the propagation delay caused by the ionospheric layer is determined based on the dual frequency reception of the first and second signals. This delay may be used to improve the accuracy of the positioning determined at step 411.

If DualFreqRecept is false, in step 412 only the first signal is detected in the baseband signal by correlation, and in step 413 the position of the receiver is determined based on the detected first signal. Among them, if the ionospheric layer determined in the previous situation where the SNR was larger than the sensitivity threshold was received at the receiver and is still up-to-date, the correction of the delay caused by the ionolayer can be performed.

The present invention enables the reception of all existing and future navigation satellite signals without increasing the complexity of the RF hardware. This improvement is due to the novel reception concept of moving two frequency channels overlapping each other. The code division multiple access feature inherent in satellite based positioning systems (and other positioning systems) due to the use of different spreading codes for signals transmitted on different frequency carriers takes this architecture into account. The basic advantages of the present invention are as follows:

Efficient dual frequency reception is possible.

-Switching between single and dual frequency reception is possible.

The use of dual frequency reception may be limited to a high SNR range in order not to degrade the performance of the reception of the more important first signal in the base channel.

Bandwidth requirement after controllable image rejection mixer is minimized.

For other GPS and Galileo navigation satellite signals, the received frequencies have L1 (having a center frequency of 1575.7 MHz) and any carrier frequency from 1176 MHz to 1227 MHz, which consists of all GPS and Galileo signals. do.

The present invention has been described above by some embodiments. It should be noted that there may be alternative ways and variations that will be apparent to those skilled in the art and may be implemented without departing from the scope and spirit of the appended claims. In particular, the present invention is not limited to receivers of satellite based positioning systems. It can be equally well placed in any other receiver that requires dual frequency reception of spread spectrum signals. In addition, the present invention is not limited to the dual frequency reception of L1 and L2 signals of GPS only. It is also possible to receive dual frequency reception of other combinations of three GPS signals L1, L2 and L5, in particular dual frequency reception of signals L2 and L5 may be particularly advantageous.

Claims (38)

In a method for dual frequency reception, Obtaining a received signal containing a first signal having a first center frequency f ₁ and a second signal having a second center frequency f ₂ ; And Processing the received signal to generate an output signal, wherein one or more types of output signal may be generated, wherein the output signal of the first type is frequency converted to a third center frequency f ₃ ; And proportional to the sum of the signal and the second signal frequency-converted to the third center frequency (f ₃ ). The method of claim 1, wherein at least two types of output signals can be generated, wherein the output signal of the second type is substantially The first signal frequency-converted to the third center frequency f ₃ , and The second signal frequency-converted to the third center frequency f ₃ How is one of them. The process of claim 1, wherein the processing of generating the output signal of the first type is And multiplying the received signal by a sinusoidal wave having a fourth center frequency (f ₄ ) to obtain the output signal of the first type. The method of claim 3, wherein f ₁ ≥ f ₂ , f ₄ = f ₂ + (f ₁ -f ₂ ) / 2 and f ₃ = f ₁ -f ₄ . 3. The processing according to claim 2, wherein said processing for generating said output signal of said second type is: Multiplying the received signal by a first sinusoidal wave having a fourth center frequency f ₄ to obtain a first mixed signal; Multiplying the received signal by a second sinusoidal wave to obtain a second mixed signal, wherein the second sinusoidal wave has the same center frequency f ₄ as that of the first sinusoidal wave and is different from the first sinusoidal wave by a first phase shift; step, Phase shifting one of the first and second mixed signals with a second phase shift to obtain a phase shifted mixed signal, and Combining the phase shifted mixed signal with the other mixed signal to obtain the output signal of the second type. The method of claim 5, wherein f ₁ ≥ f ₂ , f ₄ = f ₂ + (f ₁ -f ₂ ) / 2 and f ₃ = f ₁ -f ₄ . 6. The method of claim 5 wherein the first phase shift is [pi] / 2. The method of claim 5, wherein the second phase shift is ± π / 2. 6. The method of claim 5, wherein the phase shifted mixed signal and the other mixed signal are combined by one of addition and subtraction. 3. The output signal according to claim 2, wherein said output signal of said second type is said first signal substantially frequency-converted to said third central frequency (f ₃ ), and the quality of said first signal is determined and said at least 2 Which of the types of the output signal is produced as an output signal is determined at least in part depending on the determined quality. 11. The method of claim 10, wherein the output signal of the first type is generated if the determined quality exceeds a threshold. 3. The image processing method according to claim 2, wherein the processing for generating an output signal is performed by a mixer for frequency converting an input signal to an intermediate frequency f _IF by a frequency difference f _LO . And the video signal has the same center frequency as one of f _LO -f _IF and f _LO + f _IF . The method of claim 12, wherein the received signal is used as an input signal to the mixer, wherein f ₁ ≥ f ₂ , f _LO = f ₂ + (f ₁ -f ₂ ) / 2, and f _IF = f ₃ = f ₁ -f _LO , the output signal of the first type is generated by controlling the mixer so as not to reduce the influence of the video signal on the frequency down-converted input signal, and the output of the second type And a signal is generated by controlling the mixer to reduce the effect of the video signal on the frequency down converted input signal. 13. The method of claim 12, wherein the frequency difference f _LO is tunable. The method of claim 1, wherein the obtaining of the received signal comprises: Receiving a signal containing the first and second signals as a first antenna to obtain a first received signal, the first antenna being at least partially adapted to the first signal; Receiving a signal containing the first and second signals as a second antenna to obtain a second received signal, the second antenna being at least partially adapted to the second signal; Filtering the first received signal with a first filter structure that is at least partially adapted to the first signal to obtain a first filtered signal; Filtering the second received signal with a second filter structure that is at least partially adapted to the second signal to obtain a second filtered signal; And Combining the first and second filtered signals to obtain the received signal. 16. The method of claim 15, wherein the first filter structure comprises a bandpass filter and the second filter structure comprises a combination of lowpass and highpass filters. The method of claim 1, wherein the obtaining of the received signal comprises: Receiving a signal containing the first and second signals with a dual frequency antenna to obtain a received signal; Filtering the received signal with a first filter structure that is at least partially adapted to the first signal to obtain a first filtered signal; Filtering the received signal with a second filter structure that is at least partially adapted to the second signal to obtain a second filtered signal; And Combining the first and second filtered signals to obtain the received signal. The method of claim 1, wherein the output signal is frequency converted to a baseband center frequency. 2. The method of claim 1 wherein the first and second signals are spread spectrum signals that are each spread with different spreading codes. 20. The apparatus of claim 19, wherein the output signal is frequency converted to a baseband center frequency to obtain a baseband signal, wherein the first and second signals are in the baseband signal by correlation with their corresponding spreading codes. Method detected. The method of claim 1, wherein the first and second signals are transmitted to the receiver by at least one transmitter of at least one satellite based positioning system. 22. The method of claim 21, wherein the at least one satellite based positioning system comprises at least one of a global positioning system and a Galileo system. The method of claim 1, wherein the first frequency f ₁ is 1575.4 MHz and the second frequency f ₂ is in a range between 1176 and 1227 MHz. A computer program having instructions for causing a processor to control a receiver that performs the method steps of claim 1. A computer program product comprising a computer program having instructions that enable a processor to control a receiver that performs the method steps of claim 1. 10. A system for transmitting signals comprising at least one transmitter and at least one receiver, the at least one transmitter comprising: Means for transmitting a signal containing a first signal having a first center frequency f ₁ and a second signal having a second center frequency f ₂ , The at least one receiver, Means configured to obtain a received signal containing the first and second signals, and Means for processing the received signal to generate an output signal, the output signal of one or more types, wherein the output signal of the first type is frequency converted to a third central frequency f ₃ ; Means for proportional to the sum of one signal and said second signal frequency-converted to said third center frequency (f ₃ ). In a transmitter of a system for transmitting signals, Means for transmitting a signal containing a first signal having a first center frequency and a second signal having a second center frequency, wherein the received signal containing the first and second signals is transmitted to at least one receiver. And the received signal is processed in the at least one receiver to produce an output signal, one or more types of the output signal can be generated, and the output signal of the first type has a third center frequency (f _3). ) the frequency to convert the first signal and the third center frequency (f ₃₎ into a frequency-converted to the transmitter proportional to the sum of the second signal. A receiver for dual frequency reception, First means configured to obtain a received signal containing a first signal having a first center frequency f ₁ and a second signal having a second center frequency f ₂ ; And A second means configured to process said received signal to generate an output signal, said output signal of one or more types being capable of being frequency-converted to a third center frequency f ₃ ; And second means proportional to the sum of the first signal and the second signal frequency-converted to the third center frequency (f ₃ ). The method of claim 28, wherein the second means, Means configured to multiply the received signal with a sinusoidal wave having a fourth center frequency (f ₄ ) to obtain a first mixed signal; And Means for outputting the first mixed signal as the output signal of the first type. 29. The method of claim 28, wherein at least two types of output signals can be generated, and the output signal of the second type is substantially the first signal and the third frequency converted to the third center frequency f ₃ . Is one of the second signals frequency-converted to a center frequency f ₃ , wherein the second means comprises: Means configured to multiply the received signal with a sinusoidal wave having a fourth center frequency (f ₄ ) to obtain a first mixed signal; Means for multiplying the received signal by a second sinusoidal wave to obtain a second mixed signal, the second sinusoidal wave having the same center frequency f _{4 as} the first sinusoidal wave and a first sinusoidal wave; Other means by phase shifting; Means configured to phase shift one of the first and second mixed signals to obtain a phase shifted mixed signal; Means configured to combine the phase shifted mixed signal and the other mixed signal to obtain a combined signal; And Means for outputting the combined signal as the output signal of the second type. 29. The apparatus of claim 28, wherein at least two types of output signals can be generated, wherein the output signal of the second type is the first signal frequency converted to the third center frequency f ₃ , and the receiver comprises: Means configured to determine a quality of the first signal; And Means for determining, depending at least in part on the determined quality, whether the output signal of any of the at least two types is generated as an output signal. The method of claim 28, wherein the second means, A mixer capable of frequency converting an input signal to an intermediate frequency f _IF by a frequency difference f _LO and reducing the influence of an image signal on the frequency down-converted input signal, wherein the video signal is f _LO −. A receiver comprising a mixer having a center frequency equal to one of f _IF and f _LO + f _IF . The method of claim 32, wherein the second means, Means for inputting the received signal to the mixer. The method of claim 32, wherein the first means, A first antenna for receiving a signal containing the first and second signals to obtain a first received signal, the first antenna being at least partially adapted to the first signal; A second antenna for receiving a signal containing the first and second signals to obtain a second received signal, the second antenna being at least partially adapted to the second signal; A first filter structure for filtering the first received signal to obtain a first filtered signal, the first filter structure being at least partially adapted to the first signal; A second filter structure for filtering the second received signal to obtain a second filtered signal, the second filter structure being at least partially adapted to the second signal; And Means for combining the first and second filtered signals to obtain the received signal. 35. The receiver of claim 34 wherein the first filter structure comprises a bandpass filter and the second filter structure comprises a combination of lowpass and highpass filters. The method of claim 32, wherein the first means, A dual frequency antenna for receiving a signal containing the first and second signals to obtain a received signal; A first filter structure for filtering the received signal to obtain a first filtered signal, the first filter structure being at least partially adapted to the first signal; A second filter structure for filtering the received signal to obtain a second filtered signal, the second filter structure being at least partially adapted to the second signal; And Means for combining the first and second filtered signals to obtain the received signal. 29. The apparatus of claim 28, wherein the first and second signals are spread spectrum signals each spread with different spreading codes, and the receiver comprises: Means for frequency converting the output signal to a baseband center frequency to obtain a baseband signal; and Means for detecting the first and second signals in the baseband signal by correlation with their corresponding spreading codes. A module for dual frequency reception at a receiver, First means configured to obtain a received signal containing a first signal having a first center frequency f ₁ and a second signal having a second center frequency f ₂ ; And A second means configured to process said received signal to generate an output signal, said output signal of one or more types being capable of being frequency-converted to a third center frequency f ₃ ; And second means proportional to the sum of the first signal and the second signal frequency-converted to the third central frequency (f ₃ ).

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