Features Proven Double Conversion Architecture: First IF Capability: 10 MHz to over 1000 MHz Second IF Capability: 0.2 MHz to 2.0 MHz Dual Second IF Amplifier and Demodulator: Analog Mode Limit Amplifier and FM Quadrature Detector Band Digital Mode Linear AGC Amplifier for Dual Mixer I&Q Quadrature Demodulator n Precision Onboard LO Phase Splitters for Digital Quadrature Demodulator Pin select allows operation at minimum supply current Low supply current Provides analog Received Signal Strength Indicator (RSSI)
analog agc for digital IF amplifier
Combined voltage gain application over 100db
IS-136 (North American Dual Mode) Cellular Radio Portable and Mobile Terminal Cellular Radio Base Station Digital Satellite Communication Multiple Symbol Signal Receiver

describe
The W3030 is a monolithic integrated circuit that provides most of the receive path functions required to meet IS-136 (and IS-54) standards. The W3030 converts FM or digitally modulated IF carriers up to 200 MHz and provides the required IF gain and separate baseband detectors for both modulation modes.
W3030 is divided into three sub-functions

1. First IF mixer/amplifier
2. Analog second IF
3. Digital 2nd Mid Band (Note that the electrical spec sheet corresponds to each sub-function.)
Each section has a buffered output to allow external filtering, which also provides flexibility in system architecture choices. The first IF mixer section provides a fixed voltage conversion gain of 30dB (power gain = 17dB). The first IF mixer also performed downconversion to the 0.2mhz-2.0mhz range, which allowed the use of inexpensive ceramic filters at two points in the signal path. In the second if part, the signal path can be split between the two parallel amplifier/demodulator parts. In the second IF of the simulation, there is a 40db amplifier followed by a 60db hard limit amplifier and an fm quadrature detector (incoherent discriminator). The signal path between the 40dB and 60dB amplifier stages is taken off-chip for external filtering. In digital mode, the AGC amplifier provides 10dB to 80dB of gain. The digital signal is demodulated in a double-balanced mixer fed by an external local oscillator (lo) signal. The external lo provides the final if lo frequency by a divide-by-4 counter. This configuration greatly reduces the possibility of external lo signals being fed back to the if input, which would cause a dc offset at the i&q output. This circuit also provides a 90° phase shift of lo independent of the duty cycle. The resulting I&Q differential pair can be level shifted using the VCM input pins, providing flexibility in interfacing with digital processing ICs.
A pair of logic inputs allows the device to enter a power-down mode and one of two partially enabled modes (analog or digital only) or a fully enabled mode that allows the use of analog RSSI in digital receive mode.
Description (continued)

RSSI
The voltage level provided by the rssi output is proportional to the amount of signal present in the analog second mid-band. This voltage level is generated internally by the sum of the signal currents at various points in the 40dB and 60dB IF chain. The amount of loss between the 40db and 60db segments will affect the rssi linearity. Figure 3 contains two RSSI voltage versus IF input power curves. One trace only has filter losses between 40dB and 60dB of amplifier. The second track is a filter and a resistor with a total loss of 5.6db. The graph shows the nonlinearity around the -75 dBm input level. This non-linearity is because the 60db amplifier chain goes into compression, resulting in less rssi output. Eventually, as the input signal increases, the 40db amplifier will start to contribute to the total rssi.
It was determined that the 6db interstage loss yielded the best rssi response. The insertion loss of most ceramic filters is less than 6db. Therefore, in addition to the filter, some additional losses must be inserted. The easiest way is to use a resistor in series with the filter. This approach will result in filter mismatch and possibly distort its passband response. An L or T configuration may be required to provide the desired loss without mismatching the filter.
Amplifier Quadrature Detector The quadrature detector circuit is similar to a mixer; however, instead of mixing two different frequencies, it multiplies two signals of the same frequency, which are phase shifted. Multiplying the phase shifted with the unshifted signal produces the audio portion of the fm signal.
The quadrature detector passes the if signal through a limiter stage to produce a constant amplitude signal before applying the if signal differentially to the multiplier. The same signal is single-ended output to pin 4, ifaout. The IFOUT signal passes through the phase shifting network (CS+CP+L+R). The phase shifted signal is applied back to pin 3 of the lower half of the multiplier, quad. A parallel L/C resonant circuit provides frequency selective filtering at intermediate frequencies. The letter of credit box must be AC grounded at IF frequencies through a DC blocking capacitor (CBYpass).
Since the information in the FM signal is contained in the part off-center frequency, the design of the resonant bandpass circuit is very important, especially the load q. For a given offset, a higher load q will produce a larger output signal than a lower q circuit. However, high-q circuits allow only limited off-center frequencies before distortion occurs.
Equivalent four-slot circuit for W3030 40 kΩ input resistance. Equation 1 and Equation 2 are used to calculate the resonant frequency and the resonant cavity circuit q.
Quadrature Detectors (continued)
Four-tank S-curves One way to determine whether a tank's q-value is too large or too small is to generate a four-tank s-curve. The s-curve is the relationship between the DC audio output voltage and the IF input frequency. When the deviation from the center frequency is small, the DC audio output voltage changes proportionally. The overall linearity of the curve is determined by the q of the tank circuit; thus, q determines the allowable deviation before the audio signal is distorted. The L/C tank circuit has a shunt resistor to set the Q of the tank. The steps to draw these graphs are as follows:
1. Remove the 450 kHz IF filter and drive the input of the limiting amplifier with a signal generator capable of offm modulation.
2. Apply FM modulation and adjust tank capacitors for maximum audio output and minimum distortion.
3. While monitoring the DC voltage at the audio output, remove the FM modulation and sweep the IF frequency above or below the center frequency.
When the value of the four-slot resistor was varied from 18 kΩ to 30 kΩ with the resistor removed, the following S-curve was produced. A resistor value of 33 kΩ (corresponding to a q of 10) was chosen as the optimum resistor value.

Test circuit diagram