from the following detailed specification when read with the patent application Ser. No. 08/179,953 is hereby incorpo
accompanying drawings in which like reference numerals rated by reference in its entirety.
refer to like elements. xhe radio receiver 2 is particularly designed to receive
either wideband signals from the wideband transceiver 6 or
BRIEF DESCRIPTION OF THE DRAWINGS 5 narrowband signals from the narrowband transceivers la,
FIG. 1 is a block diagram showing the dual-mode radio lb-As discussed in detail below, the receiver 2 has a wide
receiver in accordance with the present invention employed mter bandwidth adapted to the wideband mode which filters
in a radio communication system. received radio signals when the receiver 2 is in either the
TM «. ,, , . , . ,. . narrowband or wideband mode. In the preferred
FIG. 2 is a block diagram of the dual-mode radio receiver ,n , ,. ^ ., ,. „ . j . ^.
A •,. ,u t • . • lu embodiment, the radio receiver 2 when operating in the
in accordance with the present invention. , ^_ ^ x, iL
narrowband mode extracts the narrowband signals from the
FIG. 3 is a schematic diagram depicting the processing of mtered radio signals through dig^ processing and corndigital signals in accordance with the present invention. bines the extracted narrowband signals to provide for diverDETAILED DESCRIPTION OF THE sity combination.
PREFERRED EMBODIMENTS Wlth reference t0 nG- 2< me radl° receiver 2 of the
present invention for implementing both wideband and
Referring to FIG. 1, the dual-mode radio receiver 2 of the narrowband modes is shown in more detail. The radio
present invention is shown implemented in a cellular radio receiver 2 includes a duplex filter 10 for providing the
3 having a transmitter 4 and transmit/receive (T/R) coupler transmit/receive (T/R) coupling needed to connect the
5. The radio receiver 2 has a wideband mode and a narrow- 20 receiver 2 and the transmitter 4 to the same antenna in the
band mode designed to enable radio 3 to receive radio event that the transmitter 4 and receiver 2 must operate at the
signals containing wideband frequency-modulated signals same time (Frequency Division Duplex). A T/R coupler 5
("wideband signals") and narrowband frequency-modulated can also be implemented with a T/R switch in the event that
signals ("narrowband signals"). a Time Division Duplex system is required.
More specifically, radio 3 by employing radio receiver 2 The duplex filter 10 receives radio signals that may is capable of receiving information from either a base station include wideband or narrowband signals transmitted from wideband transceiver 6 operating in accordance with a the base station transceivers 6, la, lb. The received radio wideband standard or base station narrowband transceivers signals are outputted by duplex filter 10 to low noise la, lb operating in accordance with a narrowband standard. 3Q amplifier 20. After low-noise amplification in low noise The base station wideband transceiver 6 transmits and amplifier 20, the received radio signals are outputted to a receives wideband signals and the base station narrowband downconverter 25 which can comprise an image reject filter transceivers la. lb transmit and receive narrowband signals. 30, mixer 40 and local oscillator 41. The downconverter 25 The transceivers 6, la, lb can be adapted to conform to a converts the received radio signals to a suitable first intervariety of different standards that require the use of wide- 35 mediate frequency (IF) or first downconverted signal and band or narrowband signals to transmit and receive infor- outputs the first downconverted signal to a wideband filter mation. 100.
For example, the narrowband signals can be continuous The wideband filter 100 is adapted to the wideband transmissions in a frequency division multiple access system signals transmitted by wideband transceiver 6 and restricts (FDMA) or time division multiple access transmissions 40 the signal bandwidth of the received radio signals in accor(TDMA). An example of a narrowbandTDMA system is the dance with the bandwidth of the wideband signals. The U.S. Digital cellular system conforming to the telecommu- filtered signal is outputted to an intermediate frequency (IF) nications Industry Association standard IS-54. This standard amplifier circuit 120 and additional wideband filters 110 that is incorporated by reference as an example of narrowband are adapted for the wideband signals. The wideband filters TDMA waveforms and protocols. The wideband signals can 45 100, 110 form a wideband filter apparatus 115 that estabfor example conform to the European digital cellular stan- lishes a wide signal pass bandwidth ("wide filter dard known as GSM. The GSM standard is publicly avail- bandwidth") for the receiver 2. The wide filter bandwidth of able under that name and is hereby incorporated by refer- the wideband filter apparatus 115 is adapted to filter the ence in its entirety as an example of wideband TDMA received radio signal so as to provide a filtered signal having waveforms and protocols. Alternatively, the wideband mode 50 a wide bandwidth adapted to the wideband signal, may conform to the Code Division Multiple Access system Amplifier circuit 120 includes a logarithmic amplifierdescribed in TIA standard IS-95, which is also incorporated detector chain (amplifiers 60) and a second downconverter by reference herein. 45. The amplifier circuit 120 produces an analog output
In a preferred embodiment, the base station wideband including a Radio Signal Strength Indication (RSSI) and a
transceiver 6 is land-based and the base station narrowband 55 hardlimited signal. The RSSI is an analog voltage approxi
transceiver la, lb are contained in different orbiting satellite mately proportional to the logarithm of the instantaneous
relay stations and their associated ground stations, where the amplitude of the radio signals+noise. The final amplifier 60
different satellite relay stations illuminate the same area on in the amplifier circuit 120 produces the analog hardlimited
the earth. The transmitters la, lb each transmit a narrow- signal from which a representation of instantaneous phase
band signal which contains the same speech or data infor- 60 angle of the radio signals+noise can be extracted,
mation on two different but nearby frequency channels. As The filtered signals from the amplifier circuit 120 are
disclosed in U.S. patent application Ser. No. 08/179,953, processed differently by the receiver 2 depending on
filed Jan. 11, 1994, and entitled "A Cellular/Satellite Com- whether the receiver 2 is in the narrowband mode or the
munications System With Improved Frequency Re-Use," wideband mode. When in the wideband mode, the filtered
suitable satellite configurations can be used to relay signals 65 signals are inputted into digitizer 125 as shown in FIG. 2.
from the satellites to an earth station connected to a public The digitizer 125 converts the filtered signals to digital
switched telephone network. The above-identified U.S. signals with the aid of sampling and digitizing where the