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The SA615 is a high performance monolithic low-power mixer FM IF system incorporating a mixer/oscillator, two limiting intermediate frequency amplifiers, quadrature detector, muting, logarithmic received signal strength indicator (RSSI), and voltage regulator. The SA615 combines the functions of Signetics� SA602 and SA604A, but features a higher mixer input intercept point, higher IF bandwidth (25MHz) and temperature compensated RSSI and limiters permitting higher performance application.
The SA605 and SA615 are functionally the same device types. The difference between the two devices lies in the guaranteed specifications. The SA615 has a higher I CC , lower input third order intercept point, lower conversion mixer gain, lower limiter gain, lower AM rejection, lower SINAD, higher THD, and higher RSSI error than the SA615.
I am particularly indebted to Philips Components and Semiconductors Australia for their most generous assistance in giving me access to material presented on this page.
Low power consumption: 5.7mA typical at 6V
Mixer input to >500MHz
Mixer conversion power gain of 13dB at 45MHz
Mixer noise figure of 4.6dB at 45MHz
XTAL oscillator effective to 150MHz (L.C. oscillator to 1GHz local oscillator can be injected)
102dB of IF Amp/Limiter gain
25MHz limiter small signal bandwidth
Temperature compensated logarithmic Received Signal Strength Indicator (RSSI) with a dynamic range in excess of 90dB
Two audio outputs � muted and unmuted
Low external component count; suitable for crystal/ceramic/LC filters
Excellent sensitivity: 0.22mV into 50W matching network for 12dB SINAD (Signal to Noise and Distortion ratio) for 1kHz tone with RF at 45MHz and IF at 455kHz
SA615 meets cellular radio specifications
Cellular radio FM IF
High performance communications receivers
Single conversion VHF/UHF receivers
SCA receivers
RF level meter
Spectrum analyzer
Instrumentation
FSK and ASK data receivers
Log amps
Wideband low current amplification
Here is the pin configuration of the 615 mixer FM IF system in figure 1 below.
Figure 1 - 615 mixer FM IF system pin configuration
Figure 2 - block diagram of the 615 mixer FM IF system
Vcc should lie between 4.5V DC min. and 8V DC max regulated.
Input signal frequency is typically up to about 500 Mhz, while typically the oscillator will work beyond 200 Mhz.
At 45 Mhz signal input the noise figure is quoted as 5.5 dB max although typically less than that.
Circuit Description
The SA615 is an IF signal processing system suitable for second IF or single conversion systems with input frequency as high as 1GHz.
The bandwidth of the IF amplifier is about 40MHz, with 39.7dB(v) of gain from a 50 ohm source. The bandwidth of the limiter is about 28MHz with about 62.5dB(v) of gain from a 50 ohm source. However, the gain/bandwidth distribution is optimized for 455kHz, 1.5K source applications. The overall system is well-suited to battery operation as well as high performance and high quality products of all types.
The input stage is a Gilbert cell mixer with oscillator. Typical mixer characteristics include a noise figure of 5dB, conversion gain of 13dB, and input third-order intercept of �10dBm. The oscillator will operate in excess of 1GHz in L/C tank configurations. Hartley or Colpitts circuits can be used up to 100MHz for xtal configurations. Butler oscillators are recommended for xtal configurations up to 150MHz.
The output of the mixer is internally loaded with a 1.5K resistor permitting direct connection to a 455kHz ceramic filter. The input resistance of the limiting IF amplifiers is also 1.5K. With most 455kHz ceramic filters and many crystal filters, no impedance matching network is necessary. To achieve optimum linearity of the log signal strength indicator, there must be a 12dB(v) insertion loss between the first and second IF stages. If the IF filter or interstage network does not cause 12dB(v) insertion loss, a fixed or variable resistor can be added between the first IF output (Pin 16) and the interstage network.
The signal from the second limiting amplifier goes to a Gilbert cell quadrature detector. One port of the Gilbert cell is internally driven by the IF. The other output of the IF is AC-coupled to a tuned quadrature network. This signal, which now has a 90� phase relationship to the internal signal, drives the other port of the multiplier cell.
Overall, the IF section has a gain of 90dB. For operation at intermediate frequencies greater than 455kHz, special care must be given to layout, termination, and interstage loss to avoid instability. The demodulated output of the quadrature detector is available at two pins, one continuous and one with a mute switch. Signal attenuation with the mute activated is greater than 60dB. The mute input is very high impedance and is compatible with CMOS or TTL levels.
A log signal strength completes the circuitry. The output range is greater than 90dB and is temperature compensated.
NOTE: dB(v) = 20log V OUT /V IN
Figure 3 - a possible configuration for the SA/NE615 mixer FM IF system
Figure 3 - component values for the possible configuration of the SA/NE615 mixer FM IF system
You really should download the 615 mixer data sheet - (130K) which is in PDF format. This way you get all the needed information.
You might still be able to obtain the NE/SA615 from my friend Dieter (DIZ) Gentzow - W8DIZ - Loveland, Ohio U.S.A.
Pay by PayPal or check!
NE602 or NE612 Double Balanced Mixer
615 mixer data sheet - (130K) in PDF format.
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Bibliography: - Philips Semiconductors - Semiconductors for Wireless Communications 1999 - IC17
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Updated 18th February, 2002