Intermediate frequency circuit for cellular telephone transceiver using surface acoustic wave filter
First Claim
1. An IF circuit for use in a cellular telephone receiver, comprising in combination:
- (a) a first mixer circuit receiving an rf signal from a low noise input amplifier and a first local oscillator signal from a first local oscillator circuit and producing in response thereto a first signal;
(b) a first amplifier receiving the first signal and producing an amplified second signal;
(c) a first impedance matching circuit connected to receive the second signal and match the second signal to a first impedance;
(d) a double-mode resonator SAW bandpass filter with a bandwidth of approximately 30 kilohertz and having an input connected to receive the second signal and producing a filtered third signal;
(e) a second impedance matching circuit connected to receive the third signal after it is filtered by the double-mode resonator SAW bandpass filter and impedance match it to a second input impedance;
(f) a second amplifier receiving the third signal after it has been impedance matched, and producing in response thereto a fourth signal;
(g) a second mixer circuit receiving the fourth signal and a second local oscillator signal, and producing an IF signal in response to the fourth signal and that second local oscillator signal;
(h) a first IF filter connected to receive and filter the IF signal;
(i) a third amplifier connected to receive and apply the IF signal to produce an amplified IF signal;
(j) a detector circuit connected to produce an audio frequency output signal in response to the amplified IF signal.
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Accused Products
Abstract
An IF circuit suitable for use in a cellular telephone transceiver includes a first mixer circuit receiving an rf signal and a first local oscillator signal and producing a first signal. The first signal is amplified by a first amplifier to produce an amplified second signal. A first impedance matching circuit receives the second signal and matches it to a first impedance. A double-mode resonator SAW bandpass filter with a bandwidth of approximately 30 kilohertz and a noise figure less than 5 dbm produces a filtered third signal in response to the second signal. A second impedance matching circuit is connected to receive the third signal after it is filtered by the double-mode resonator SAW bandpass filter, and impedance matches it to a second impedance. A second amplifier receives and amplifies the third signal. A second mixer circuit receives the fourth signal and a second local oscillator signal, and produces an IF signal.
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Citations
9 Claims
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1. An IF circuit for use in a cellular telephone receiver, comprising in combination:
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(a) a first mixer circuit receiving an rf signal from a low noise input amplifier and a first local oscillator signal from a first local oscillator circuit and producing in response thereto a first signal; (b) a first amplifier receiving the first signal and producing an amplified second signal; (c) a first impedance matching circuit connected to receive the second signal and match the second signal to a first impedance; (d) a double-mode resonator SAW bandpass filter with a bandwidth of approximately 30 kilohertz and having an input connected to receive the second signal and producing a filtered third signal; (e) a second impedance matching circuit connected to receive the third signal after it is filtered by the double-mode resonator SAW bandpass filter and impedance match it to a second input impedance; (f) a second amplifier receiving the third signal after it has been impedance matched, and producing in response thereto a fourth signal; (g) a second mixer circuit receiving the fourth signal and a second local oscillator signal, and producing an IF signal in response to the fourth signal and that second local oscillator signal; (h) a first IF filter connected to receive and filter the IF signal; (i) a third amplifier connected to receive and apply the IF signal to produce an amplified IF signal; (j) a detector circuit connected to produce an audio frequency output signal in response to the amplified IF signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method of producing an amplified IF signal in a cellular telephone receiver, the method comprising the steps of:
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(a) applying an rf signal having a signal strength of-116 dbm to-30 dbm to an input amplifier; (b) applying an output signal produced by the first input amplifier and a first local oscillator signal to a first mixer circuit to produce a first signal; (c) applying the first signal to produce an amplified second signal; (d) impedance matching the second signal to a first impedance; (e) filtering the second signal with a double-mode resonator SAW bandpass filter to produce a filtered third signal, the double-mode resonator SAW bandpass filter having a bandwidth of approximately 30 kilohertz and an insertion loss of less than 5 db; (f) impedance matching the third signal to a second impedance after the third signal is filtered by the double-mode resonator SAW bandpass filter; (g) amplifying the third signal after it has been impedance matched to produce a fourth signal; (h) applying the fourth signal and a second local oscillator signal to a second mixer circuit to produce an IF signal; (i) filtering the IF signal by means of a first IF filter connected to receive and filter the IF signal; (j) amplifying the IF signal to produce the amplified IF signal, and whereby the amplified IF signal can be applied to a quadrature detector circuit to produce an audio frequency output signal.
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Specification