A payload of a communications satellite includes several receive chains connected to respective antennas 1 to 4. Each receive chain 6 is hybrid in that analogue filtering is carried out at the front end in order to remove the unwanted input spectrum beyond that of a broadband within which a narrowband signal is frequency hopped. Thereafter the filtered signal is digitized and the hopping pattern removed by using successive segments of a control word which determines the hopping frequencies to successively select progressively narrower sub-bands which contain the wanted signal on each hop.
The digital frequency-hopping (FH) transceiver and the method thereof can be applied to FH communication system with a short FH time. The transceiver employs a digital signal processing (DSP) in baseband (BB) circuits to implement FH without need to adjusting the RF carrier frequency. Wherein, the digital FH transmitter performs DSP on a digital BB transmission signal to frequency-hop between BB sub-bands corresponding to sub-bands of a channel, converts it into an analog signal, and then modulates the analog signal to the channel sub-bands for transmission. The digital FH receiver then performs carrier demodulation, analog-to-digital conversion and DSP on a received signal to regain the original digital BB transmission signal.
A signal analyzer to characterize the RF signal transmitted by a frequency hopping radio transmitter. The transmitted signal is analyzed while hopping across a broad frequency band without knowledge of the hop frequencies, timing or signal bandwidth. A wide range of signal parameters are measured on the dehopped signal to characterize the radio performance and the compliance to the radio specifications.
The present invention relates to an arrangement (1) and a method in a receiver in a multi-mode mobile radio (m), wherein the intention is to design the receiver so that it uses the same hardware to process several different channel bandwidths corresponding to the different networks used by the radio (m). This is done by changing a sampling frequency (f.sub.s) which controls a digital filter unit (25) situated in the digital part of the receiver. The changing of the sampling frequency (f.sub.s) results in that the bandwidth of the digital filter unit (25) is scaled accordingly, wherein the desired channel bandwidth at baseband of the radio network (GSM1900, AMPS) to be used by the radio (m) is selected in the digital filter unit (25). As a complement, the digital filter unit (25) can be implemented with a programmable function, where a change of parameters and/or filter structure inside the digital filter unit (25) can be used to adjust the filter bandwidth.
A low pass digital filter using cascade polyphase recursive digital signal processing circuit. The filter in the receive direction may contain a re-sampling Hogenauer filter followed by an equalizer filter to correct for its non-flat pass-band spectral response. The output of the spectral equalizer may be processed by a poly-phase re-sampling filter to reduce the sample rate. A clean-up filter may insert two stop-band spectral intervals in the frequency response of the earlier stages. The filter in the receive direction may be implemented by using similar components in the reverse order.
A dual mode filter for mobile communication may implement two disparate cellular systems such as GSM and W-CDMA. The same transceiver may be utilized to selectively receive and transmit in either of the two systems. When the system is in a GSM area, the system sends and receives GSM signals using programmable filters. Two cascaded digital decimation filters may substitute for one narrow band digital decimation filter in conventional designs. One of the filters is a multi-band digital decimation filter with N bands and the other of the digital filters is used to reject the N-1 multi-band of the system. The number of taps on each filter may selectively be set to implement either GSM or W-CDMA. In addition, the output for the system may be set to be the output of the first filter, in the case of a W-CDMA system, or the combination of the two cascaded filters in a GSM system.
