HSP50214BVCZ datasheet(8/62 Pages) RENESAS

8 / 62 page

HSP50214B

FN4450 Rev 4.00

Page 8 of 62

May 1, 2007

the ability to change the received signal gain and frequency,

synchronous with burst timing. The synchronous gain

adjustment allows the user to measure the power of the signal

at the A/D at the end of a burst, and synchronously reload that

same gain value at the arrival of the next user burst.

For applications other than cellular phones (where the

preambles are not changed), the PDC frequency

discriminator output can be used to obtain correlation on the

preamble pattern to aid in burst acquisition.

Several applications are combinations of frequency and time

domain multiple access schemes. For example, GSM is a

TDMA signal that is frequency hopped. The individual

channels contain Gaussian MSK modulated signals. The

PDC again offers the 0.012Hz tuning resolution for de-

hopping the received signal. The combination of halfband

and 256-tap programmable, 22-bit coefficient FIR filters

readily performs the necessary matched filtering for

demodulation and optimum detection of the GMSK signals.

CDMA Based Standards and Applications

For Code Division Multiple Access (CDMA) type signals, the

PDC offers the ability to have a single wideband RF front

end, from which it can select a single spread channel of

interest. The synchronization circuitry provides for easy

control of multiple PDC for applications where multiple

received signals are required, such as base-stations.

In IS-95 CDMA, the receive signal bandwidth is

approximately 1.2288MHz wide with many spread spectrum

channel in the band. The PDC supplies the downconversion

and filtering required to receive a single RF channel in the

presence of strong adjacent interference. Multiple PDC’s

would be sourced from a single receive RF chain, each

processing a different receive frequency channel. The

despreader would usually follow the PDC. In some very

specific applications, with short, fixed codes, the filtering and

despreading may be possible with innovative use of the

programmable, 22-bit coefficient FIR filter. The PDC offers

0.012Hz resolution on tuning to the desired receive channel

and excellent rejection of the portions of the band not being

processed, via the halfband and 255-tap programmable, 22-

bit coefficient FIR filter.

Traditional Modulation Formats

AM, ASK, FM AND FSK

The PDC has the capability to fully demodulate AM and FM

modulated waveforms. The PDC outputs 15-bits of amplitude

or 16-bits of frequency for these modulation formats. The FM

discriminator has a 63-tap programmable, 22-bit coefficient FIR

filter for additional signal conditioning of the FM signal. Digital

versions of these formats, ASK and FSK are also readily

processed using the PDC. Just as in the AM modulated case,

ASK signals will use 15-bit magnitude output of the Cartesian to

Polar Coordinate converter. Multi-tone FSK can be processed

several ways. The frequency information out of the

discriminator can be used to identify the received tone, or the

filter can be used to identify and power detect a specific tone of

the received signal. AMPS is an example of an FM application.

PM AND PSK

The PDC provides the downconversion, demodulation,

matched filtering and coordinate conversion required for

demodulation of PM and PSK modulated waveforms. These

modulation formats will require external carrier and symbol

timing recovery loop filters to complete the receiver design.

The PDC was designed to interface with the HSP50210

Digital Costas Loop to implement the carrier phase and

symbol timing recovery loop filters (for continuous PSK

signals-not burst).

Digital modulation formats that combine amplitude and

phase for symbol mapping, such as m-ary QAM, can also be

downconverted, demodulated, and matched filtered. The

received symbol information is provided with 16-bits of

resolution in either Cartesian or Polar coordinates to

facilitate remapping into bits and to recover the carrier

phase. External Symbol mapping and Carrier Recovery

Loop Filtering is required for this waveform.

Resampling and Interpolation Filters

Two key features of the resampling FIR filter are that the re-

sampler filter allows the output sample rate to be

programmed with millihertz resolution and that the output

sample rate can be phase locked to an independent

separate clock. The re-sampler frees the front end sampling

clocks from having to be synchronous or integrally related in

rate to the baseband output. The asynchronous relationship

between front end and back end clocks is critical in

applications where ISDN interfaces drive the baseband

interfaces, but the channel sample rates are not related in

any way. The interpolation halfband filters can increase the

rate of the output when narrow frequency bands are being

processed. The increase in output rate allows maximum use

of the programmable FIR while preserving time resolution in

the baseband data.

TABLE 2. CELLULAR BASESTATION APPLICATIONS USING



TDMA

STANDARD

GSM

PCN

IS-54

TYPE

Cellular

BASESTATION RX

BAND (MHz)

935-960

1805-1880

824-849

CHANNEL BW (kHz)

200

# TRAFFIC CHANNELS

VOICE MODULATION

GMSK

/4

DQPSK

CHANNEL RATE (Kbps)

270.8

48.6

CONTROL

MODULATION

GMSK

/4

DQPSK

CHANNEL RATE (Kbps)

270.8

48.6

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