WO2010017180A1

WO2010017180A1 - A bi-directional repeater with a single local oscillator and frequency synthesizer

Info

Publication number: WO2010017180A1
Application number: PCT/US2009/052671
Authority: WO
Inventors: Scott Terry
Original assignee: Wireless Extenders, Inc.
Priority date: 2008-08-04
Filing date: 2009-08-04
Publication date: 2010-02-11

Abstract

The invention relates to a bi-directional repeater with a single local oscillator and a single frequency synthesizer. The bi-directional repeater includes an uplink circuit for amplifying signals from a mobile device to a base station and a downlink circuit for amplifying signals from the base station to the mobile device. A single local oscillator signal generation circuit is used to generate a local oscillator signal. The local oscillator signal is used for frequency conversions in both the uplink circuit and the downlink circuit.

Description

A BI-DIRECTIONAL REPEATER WITH A SINGLE LOCAL OSCILLATOR AND

FREQUENCY SYNTHESIZER

BACKGROUND OF THE INVENTION The present invention relates to wireless communication. More specifically, the present invention relates to repeaters used in wireless communications networks.

Cellular communication is one of the widely used types of wireless communication. In cellular communication systems, a geographical area is divided into a plurality of cells. Each cell has a base station that communicates with one or more mobile devices in the cell. Signals transmitted from the base station to a mobile device are known as downlink signals. Signals transmitted from the mobile device to the base station are known as uplink signals.

In cellular communication networks, there exist areas within a cell where the reception of downlink signals from the base station to a mobile device may be poor. Such areas may include, but are not limited to, tall buildings, car parking basements and residential areas with poor signal coverage. Mobile devices operating in such areas often face connectivity problems that result in frequent call interruptions. Hence, wireless devices such as repeaters are used to improve the signal coverage in such areas. A repeater amplifies downlink signals from a base station and re-transmits them to the mobile device. Likewise, the repeater amplifies uplink signals from a mobile device and re-transmits them to the base station.

Existing repeaters use two pairs of local oscillators and frequency synthesizers. One pair of local oscillator and frequency synthesizer is used for the downlink circuit and the other pair is used for the uplink circuit. However, use of two pairs of local oscillators and frequency synthesizers considerably increases power consumption of the bidirectional repeater. Further, the printed circuit board (PCB) real state required is greatly increased. Hence, the hardware cost also increases. Moreover, use of two pairs of local oscillators and frequency synthesizers leads to an increase in the harmonics generated in the circuit. In light of the foregoing discussion, there is a need for a repeater with reduced power consumption. Further, there is a need for a repeater circuit that occupies less space on a PCB. Moreover, there is a need for a repeater with fewer active components like local oscillator, frequency synthesizer, etc that contribute to the harmonics in the circuit.

SUMMARY

An object of the present invention is to provide a bi-directional repeater with a single local oscillator and a single frequency synthesizer.

To achieve the above-mentioned objective, various embodiments of the present invention provide a bi-directional repeater for amplifying signals between a base station and a mobile device. The bi-directional repeater includes an uplink circuit for amplifying signals from a mobile device to a base station and a downlink circuit for amplifying signals from the base station to the mobile device. A single local oscillator signal generation circuit is used to generate a local oscillator signal. Further, a single frequency synthesizer is used to vary the frequency of the local oscillator signal.

The use of a single local oscillator and a single frequency synthesizer considerably reduces power consumption of the chip on which the bi-directional repeater is integrated. Further, the number of electrical components mounted on a printed circuit board (PCB) is reduced. Hence, the hardware cost is lowered. Moreover, use of only one local oscillator reduces the harmonics generated in the circuit. Use of fewer active components further improves the reliability of the product.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the invention will hereinafter be described in conjunction with the appended drawings provided to illustrate and not to limit the invention, wherein like designations denote like elements, and in which:

The figure is a block diagram of a bi-directional repeater, in accordance with an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

Various embodiments of the present invention provide a bi-directional repeater for amplifying signals between a base station and a mobile device. The bi-directional repeater includes an uplink circuit for amplifying signals from a mobile device to a base station and a downlink circuit for amplifying signals from the base station to the mobile device. A single local oscillator signal generation circuit is used to generate a local oscillator signal. The local oscillator signal is used for frequency conversions in both the uplink circuit and the downlink circuit.

The figure is a block diagram of a bi-directional repeater 100 in accordance with an embodiment of the present invention. Bi-directional repeater 100 comprises a downlink circuit 102, an uplink circuit 104, a tower side antenna 106, a mobile side antenna 108, a plurality of duplexers, such as duplexer 1 10a and duplexer 1 10b, a local oscillator signal generation unit 1 12, a central processing unit (CPU) 114 and a memory device 1 16. Local oscillator signal generation unit 1 12 comprises a local oscillator 1 18, a frequency synthesizer 120 and a reference oscillator 122. Downlink circuit 102 comprises a plurality of downlink filters, such as downlink filters 124a and 124b, downlink mixer 126a, downlink up-converter 128a, a downlink intermediate frequency (IF) filter 130a and a downlink power amplifier 132a. Uplink circuit 104 comprises a plurality of uplink filters, such as uplink filters 134a and 134b, an uplink mixer 126b, an uplink up-converter 128b, an uplink IF filter 130b and an uplink power amplifier 132b.

Tower side antenna 106 receives downlink signals from a base station and carries them to downlink circuit 102 for further processing through duplexer 1 10a. Tower side antenna 106 receives uplink signals from uplink circuit 104 through duplexer 1 10a and radiates them to the base station. Mobile side antenna 108 also receives uplink signals from a mobile device and carries them to uplink circuit 104 for further processing through duplexer 1 10b. Mobile side antenna 108 also receives downlink signals from downlink circuit 102 through duplexer 1 10b and radiates them to the mobile device.

Downlink filter 124a filters the downlink signal frequencies to pass the entire downlink signal band in which a mobile device is operating. Local oscillator 1 18 generates a local oscillator signal, and frequency synthesizer 120 varies the frequency of the local oscillator signal using reference oscillator 122. The downlink signal and the local oscillator signal are mixed by downlink mixer 126a and filtered by downlink IF filter 130a to generate a downlink IF signal that represents the desired RF sub band. The downlink IF signal is then mixed with the local oscillator signal by downlink up-converter 128a and filtered by downlink filter 124b to re-generate the downlink signal. Subsequently, the downlink signal is amplified by downlink power amplifier 132a. Mobile side antenna 108 receives the amplified downlink signal through duplexer 1 10b and radiates the amplified downlink signal to the mobile device.

Uplink filter 134a filters the uplink signal frequencies to pass the entire uplink signal band in which the mobile device is operating. Local oscillator 118 generates a local oscillator signal, and frequency synthesizer 120 varies the frequency of the local oscillator signal using reference oscillator 122. The uplink signal and the local oscillator signal are mixed by uplink mixer 126b and filtered by uplink IF filter 130b to generate an uplink IF signal that represents the desired RF sub band. The uplink IF signal is then mixed with the local oscillator signal by uplink up-converter 128b and filtered by uplink filter 134b to re-generate the uplink signal. Subsequently, the uplink signal is amplified by uplink power amplifier 132b. Tower side antenna 106 receives the amplified uplink signal through duplexer 1 10a and radiates the amplified uplink signal to the base station. In various embodiments of the present invention, downlink filters 124a and 124b and uplink filters 134a and 134b may be RF filters.

CPU 1 14 determines a frequency plan of bi-directional repeater 100. In an embodiment, the frequency plan is a set of frequencies based on which CPU 1 14 instructs frequency synthesizer 120 to vary the frequency of the signal generated by local oscillator 118. In an embodiment, the frequency plan is based upon the standard in which bi-directional repeater 100 is operating. In various embodiments of the present invention, bi-directional repeater 500 may operate according to the standard such as, Universal Mobile Telecommunications System (UMTS), Global System for Mobile communications (GSM), Code Division Multiple Access (CDMA), High Speed Downlink Packet Access (HSDPA), Evolution-Data Optimized (EVDO), Long term evolution (LTE) and Worldwide Interoperability for Microwave Access (WiMAX) standards and so forth. For example, an exemplary frequency plan of bi-directional repeater 100 operating in UMTS standard shall comprise one or more frequencies in the frequency range 1885 MHz to 2025 MHz for uplink signals and in the frequency range 2110 to 2200 MHz for downlink signals. Similarly, an exemplary frequency plan of bi-directional repeater 100 operating in personal communications service (PCS) sub-band shall comprise one or more frequencies in the frequency range 1850 MHz to 1910 MHz for uplink signals and in the frequency range 1930 MHz to 1990 MHz for downlink signals.

Memory device 116 stores a plurality of frequency plans that may be used by the repeater. Based on the frequency plan, CPU 1 14 instructs frequency synthesizer 120 to vary the frequency of the local oscillator signal generated by local oscillator 1 18. The local oscillator signal is used for up-conversion and down-conversion in both downlink circuit 102 and uplink circuit 104. Bandwidths of downlink IF filter 130a and uplink IF filter 130b are chosen according to the downlink IF signal and uplink IF signal generated.

The functioning of bi-directional repeater is explained with the help of the following example. When bi-directional repeater is operating in the PCS sub-band, downlink signal range is from 1930 MHz to 1990 MHz. For a downlink signal centered around 1962.6 MHz, downlink intermediate frequency (IF) is chosen as 380 MHz. Hence, CPU 1 14 instructs synthesizer 120 to generate a local oscillator signal of 1542.6 MHz. Downlink mixer 126a mixes the local oscillator signal and the downlink signal to generate a downlink signal of 380 MHz. Downlink IF filter 130a filters the downlink IF signal. The bandwidth of downlink IF filter 130a is chosen as 5 MHz. Downlink up- converter 128a converts the downlink IF signal using the local oscillator signal to regenerate the downlink signal of 1962.6 MHz. Downlink power amplifier 132a amplifies the downlink signal. Mobile side antenna 108 receives the amplified downlink signal through duplexer 1 10b and radiates the amplified downlink signal to the mobile device.

In this example, the uplink signal range is from 1850 MHz to 1910 MHz for the PCS sub-band. The uplink signal range is offset by an approximate margin of 80.04 MHz from the downlink signal. Hence, the uplink signal frequency is 1882.56 MHz. Uplink mixer 126b mixes the local oscillator signal generated by local oscillator 1 18 and the uplink signal to generate uplink IF signal of 339.96 MHz. The local oscillator signal is used for up-conversion and down-conversion in both downlink circuit 102 and uplink circuit 104. Uplink IF filter 130b filters the uplink IF signal. The bandwidth of uplink IF filter 130b is chosen as 5 MHz. Uplink up-converter 128b converts the uplink IF signal using the local oscillator signal that was used to re-generate the downlink signal, to regenerate the uplink signal of 1882.56 MHz. Uplink power amplifier 132b amplifies the uplink signal. Tower side antenna 106 receives the amplified uplink signal through duplexer 1 10a and radiates the amplified uplink signal to the base station.

Various embodiments of the present invention have numerous advantages. The use of a single local oscillator and a single frequency synthesizer considerably reduces power consumption of the chip on which the bi-directional repeater is integrated. Further, the printed circuit board (PCB) space required is reduced. Hence, the hardware cost is lowered. Moreover, use of only one local oscillator frequency reduces the harmonics generated in the circuit. Use of fewer active components further improves the reliability of the product.

While various embodiments of the invention have been illustrated and described, it will be clear that the invention is not limited to these embodiments only. Numerous modifications, changes, variations, substitutions and equivalents will be apparent to those skilled in the art without departing from the spirit and scope of the invention as described in the claims.

Claims

What is claimed is:

1. A bi-directional repeater, the bi-directional repeater comprising: a downlink circuit, the downlink circuit amplifying signals from a base station to a mobile device; an uplink circuit, the uplink circuit amplifying signals from the mobile device to the base station; and a single local oscillator signal generation circuit connected to each of the downlink circuit and the uplink circuit, the local oscillator generation circuit comprising: a local oscillator generating a local oscillator signal; a reference oscillator ; and a frequency synthesizer, the frequency synthesizer varying a frequency of the local oscillator signal using the reference oscillator.

2. The bi-directional repeater according to claim 1 further comprising a central processing unit (CPU), the CPU programming the frequency of the frequency synthesizer.

3. The bi-directional repeater according to claim 1 further comprising a memory, the memory storing a plurality of local oscillator frequencies.

4. The bi-directional repeater according to claim 1 , wherein the downlink circuit further comprises: at least one downlink filter, the at least one downlink filter filtering a plurality of downlink signal frequencies; a downlink mixer, the downlink mixer mixing the downlink signal and the local oscillator signal to generate a downlink intermediate (IF) signal; a downlink IF filter, the downlink IF filter, filtering the downlink IF signal; a downlink up-converter, the downlink up-converter converting the downlink IF signal to a downlink RF signal using the local oscillator signal; and a downlink power amplifier, the downlink power amplifier amplifying the downlink signal.

5. The bi-directional repeater according to claim 1 , wherein the uplink circuit further comprises: at least one uplink filter, the at least one uplink filter filtering a plurality of uplink signal frequencies; an uplink mixer, the uplink mixer mixing the uplink signal and the local oscillator signal to generate an uplink intermediate frequency (IF) signal; an uplink IF filter, the uplink IF filter filtering the uplink IF signal; an uplink up-converter, the uplink up-converter converting the uplink IF signal to an uplink RF signal using the local oscillator signal; and an uplink power amplifier, the uplink power amplifier amplifying the uplink signal.

6. The bi-directional repeater according to claim 1 further comprising a tower side antenna for transmitting uplink signals to the base station and receiving downlink signals from the base station.

7. The bi-directional repeater according to claim 1 further comprising a mobile side antenna for transmitting downlink signals to the mobile device and receiving uplink signals from the mobile device.

8. The bi-directional repeater according to claim 1 , wherein the bi-directional repeater operates according to at least one of the Universal Mobile Telecommunications

System (UMTS), Global System for Mobile communications (GSM), Code Division Multiple Access (CDMA), High Speed Downlink Packet Access (HSDPA), Evolution- Data Optimized (EVDO), Long term evolution (LTE) and Worldwide Interoperability for Microwave Access (WiMAX) standards.